K-On!/WMG

Yui is Tyler Durden.
The other characters are merely.

This theory can be traced to here and here.

Mugi is Tyler Durden
This would explain why she's always trying to get people to hit her.

Yui and Ui's parents are Secret Agents.
It is the only explanation for why they would be out of the country so often (i.e. all the time) and still getting paid enough to send money home to their children.
 * Jossed, they're travel agents.
 * Or so they claim.
 * They're secret travel agents.

Following that Yui and Ui's parents are Secret Agents, Ui is an Android
Built to take care of their only daughter in their absence.

The Anime and the Manga are Alternate Universes
Alright, this is a pretty minor WMG. Every adaption has a few minor differences in story telling and so on, but before you go "Oh, you could say that about any Anime of the Manga!"... how would you explain Satoshi, who only shows up in the anime, otherwise? That "added bonus" that Ritsu had in the Christmas episode? Speaking of which, considering how Ritsu is related to both of those things...
 * I can dig it:
 * Azusa, from the little I've seen of her anime version, seems a lot more subdued than her manga counterpart, who we first see gushing about the band/club.
 * When they first went to get Yui her guitar, they found it much more expensive than Yui had gotten an advance for. In the anime, Ritsu mentioned haggling, and had to explain it to Tsumugi. Then they got a part-time job, and when that was done, they went back, and Tsumugi went to the clerk to "haggle". In the manga, no such explanation takes place, and there is no part-time job; Tsumugi simply goes and asks for the price to be lowered.

As an Alternative to the above WMG, the Anime is less focused on Yui's POV
The first episode was based mainly on how Yui saw the world because we had to be introduced to the characters. Slowly, the camera started to pan away from Yui and to either everybody or Ritsu. Yui would probably not be the type to remember such an incident as the photos in the Christmas episode, and while she did know that Ritsu had a younger brother (she only reacted negatively to Ritsu not coming to the hotpot because of Satoshi, and did not ask about him) she simply didn't care because of them not sharing any classes or club time. This could also explain why Tsumugi's hinted "dark side" isn't shown in the anime - in one case only Mio and her butler gets to hear about it, and in another only Azusa seems to notice the Death Glare that she gives a music shop worker. Now whose point of vision is this?

It might be somebody who stalks the band as a whole, not any of the individuals. Said stalker might be a journalist who also interviews them once in a while shortly after their graduation, and then writes down everything he/she hears. Because the journalist is only human, he/she might miss out a few things, or even he/she first drew the manga, and then upon continued research and remembering more, started on the anime.

Yui is Kyon's little sister.
This is very, very obvious in the flashback scenes. Just look at her! On the bright side, at least now we know where Haruhi's friend got his name from.
 * The problem with this is the existence of Yui's younger sister Ui. She is one year younger than Yui so she would have been about 9 or 10 during the events of the Suzumiya Haruhi novels. Kyon never mentions her though.
 * A wizard did it.
 * Since Haruhi is shown to love little kids, it would have made more sense if she would have wished Ui into existence right away.
 * It's obvious that Ui is actually a doppelgander of Yui from an alternate dimension (offset by one year) that Kyon had to bring along with him after screwing up horribly during one of his unwelcome adventures. Thus why they treat each other like twins. Obviously in this alternate dimension circumstances forced Yui/Ui to become far more responsible and mature- which is why she enjoys seeing her alternate self so carefree and happy go lucky.
 * We already know that Kyon's sister is Mikuru, so if Yui is Li'l Sis is Mikuru, then Yui is a time traveler, which provides numerous possible explanations for Ui.
 * Episode 13 showed a Zeppelin in the sky around the 8:25 mark, right after Yui buys a steamed meat bun. Being Genre Savvy, Haruhi knows that Zeppelins signify alternate universes. The implications are obvious, that she's made minor changes (Hah! Music pun!) in the world to make it more interesting.
 * Kyon's name is now Gitah. That's why she won't play using her teeth. It'd just be wrong.

Yui has spinocerebellar ataxia type-13.
Lack of coordination? Check. Involuntary eye movements? Check. Dysarthria? Check. Mental retardation? Check.
 * Since when do mentally retarded people get perfect test scores in high school? Dysarthria is out too, since her speech is just fine. She also has sufficient muscle control to play a guitar. She's just inattentive and clumsy, but nothing on a pathological scale.
 * There's another theory that Yui has Williams syndrome: lack of social inhibition, "elfin" facial features, perfect pitch, developmental delay.
 * Dude, that page just perfectly described Yui. Awesome!
 * This means she would have a variety without mental retardation, since she is able to attend a prestigious high school—which is extremely rare. She doesn't seem to be overly sociable outside of her own group (although it's hard to tell) and her motor skills are just fine. Perfect pitch is also not super rare among "normal" people. Yui looks exactly the same as Ui, who lacks any of the signs of the syndrome. To me, Yui would qualify more for a mild version of ADHD, but nothing on a pathological scale.
 * "She doesn't seem to be overly sociable outside of her own group" -- On the contrary, the episode where they do their first club gig, and all the other bands look hostile and/or dangerous, Yui marches in and turns them all into friends in minutes. Yui is socially fearless.

All the band's girls are Vocaloids/Instrument Simulators of some sort.
It would make some sense, if we think about it.
 * How?
 * Don't ask. It's WMG, everything makes sense at some point. I'd say everyone in the entire world is a robot, but...
 * The theory would almost seem plausible if it weren't for the fact that they sound like actual humans, while the Vocaloids have a weird Uncanny Valley effect to their voices.
 * The second season OP, "Go! Go! Maniac", is the first song that actually sounds better performed by a Vocaloid.
 * Rather, they are the templates for upcoming vocaloid voicefonts.
 * I don't know, the current vocaloids seem to fit just fine.
 * They're Mark II Vocaloids, more capable of infiltration of rock bands for purposes of assimilating potential future rebels against the coming Moe invaders. At this point, only dogs and music critics can out them.

The events in the series are pre-recession.
The after-school job that the girls get as traffic takers is ridiculously easy, and would be filled even before reaching the classified section. Mugi's the daughter of the president of a guitar company and her family has a large villa over the beach, where even her family members need appointments to get in! Yui's parents seem to travel around the world... all the time. Also, the girls spend tons of money during their after-school time just buying more food and doing other activities instead of actually practicing.
 * The series takes place somewhere between 2006 and 2009. The headphones Mio wears in episode 5 are AKG K701s. AKG released the model in 2006. So it's very possible that it takes place before the current recession, but it certainly does not take place before the Japanese economic crash in the 90s (the cast's cell phones are more than enough proof of that). It's slightly less likely that it actually did take place in 2006 as the K701s were going for $400 US at the time. It's more likely that it happens in 2007-2008; around that time, Internet prices of the K701s were down to a much more reasonable ~$250 US.
 * Yes, it would apply to the current recession obviously- a lot more would be different than just the cell phones if it were to take place in the 1990s! Besides, with the prices so high, that would compel the characters to bargain all the more for their equipment!

Yui is somehow related to Hayate Yagami.
First thought on seeing her was, "Isn't that Hayate?" Not much meat to go on, but still.
 * Well, they seem to share a love for dressing up and have that hair pin right there. Alternatively,
 * It seems someone thinks Hayate is K-On-isible too.
 * Going with the cosplay idea, Sawako would be (related to) Carim?

Yui is actually Hayate from an AU where the Book of Darkness doesn't exist.
In this universe, the Book of Darkness never existed, meaning that Vita, Signum, and the other knights don't either. This means that Nanoha and Fate were never forced to battle with them. As such, she never met the two. Also, in this universe, Hayate was mysteriously renamed Yui and had a sister. Also, Section 6 is now screwed due to the lack of a captain and powerful artillery support.

Azusa is Kooh from Pangya all grown up.
Kooh finally gave up looking for her dad and got bored of being a... golfing pirate. Plus, the hair! The nekomimi!

The girls are all the girls from Lucky Star in a new reality.
Just as Konata was once Haruhi Suzumiya before she destroyed reality and remade herself into a (somewhat) normal otaku girl, she eventually grew bored again and remade herself as Ritsu, Kagami as Mio, Tsukasa as Yui, Miyuki as Mugi, Kuroi as Sawako-sensei, and Yutaka as Azusa. Though she actually split Kagami's mind, giving Azusa the dere-dere and Mio the tsun-tsun.

Yui and Ui are twins.
As You Know, Yui and Ui are actually pretty similar to each other, to the extent that Ui can easily pass for her sister just by letting her hair down. Due to how school years work in Japan, everybody born before the date in which a school year begins can enroll; whoever is born on or after that date has to wait for the next school year. Twins aren't born at the same time, there's a delay between the two births, which can sometimes last a couple of hours. Ergo: Yui is the eldest twin, born just before midnight; Ui is the youngest twin, born just after midnight. Owing to what has been explained above, Yui has been enrolled in school one year earlier than her sister, despite their age difference being at most a couple of hours.
 * They also exhibit the extreme closeness that is typical for most identical twins.
 * Perhaps when she was little, Ui was very sick and missed a large part of one school year, causing her to fall back a grade. Hey, it still happens sometimes even in these days of modern medicine.
 * Unfortunately, this one's Jossed. According to the DVD box set, Yui's birthday is November 27, and Ui's is February 22.
 * W-w-w-wait a minute, does that mean Yui and Ui are only about 3 months apart? How is that even possible?
 * But it's elementary, my dear troper. You see, Ui is actually the eldest daughter, while Yui is the youngest, making Ui older than Yui by about nine months; thus, they should have been in the same class. However, because of their parents' prolonged absence, Ui was forced by her sense of responsibility to take care of her younger sister, and was held back a year in primary school as a consequence of not being able to focus on her schoolwork. Also, being young when their parents left them, they forgot who was the eldest, and they assumed Yui was the eldest because she was one year ahead of Ui in school. It makes sense. Actually, I think this is a pretty good WMG on its own, so I'm gonna go copy-paste what I've just written in a new entry.
 * Perhaps they are indeed twins biologically speaking, buy Yui got born three months premature (which explains why Yui is a little bit 'special'), while Ui was brought to full term. Ui, upon learning this, then made it her life goal to serve her onee-chan to alliviate the guilt of kicking her sister out of mommy's womb.
 * Although delayed interval delivery is possible, the actual likely hood of it being this is pretty slim, the longest recorded delay in history is 110 days. Most of the time the first twin dies. If this had really happened, their birth would be a big deal, and it would've been mentioned at some point. Yui is just 15 months older.
 * The above explanation would certainly make a lot of sense, unless the DVD Box Set also mention the years that is. In Japan school terms (or school years) starts in April, thus if Yui and Ui are indeed only 3 months apart, they'd be in the same grade, thus it's better explained if they are 15 months apart instead.
 * Explanation is simple : Japanese school year start on April 1 and end on March 31. Anyone who have his Xth birthday during school year will only be with people who reach the same criteria. So they are 15 month apart.
 * Ui was in an horrible accident in middle school (her legs are actually highly developed prosthetics and since her eyes are prototypes similar to that of, she used them to play guitar by just looking at her sister playing it) and since she had to spend couple of months in rehab, she just repeated the grade.

The girls of K-ON! are the girls of Ichigo Mashimaro, a few years later.
Miu is Ritsu, Chika is Mio, Ana is Mugi, and Matsuri is Yui.
 * This troper has a pikachure to back that one up.

The series is a metaphorical satire of the decadence of rock'n'roll.
Cakes = drugs.
 * Win.
 * "Mugi-chan, could I have some more * ahem* sugar with my tea?"
 * "Just follow me to the back, and I'll hook you up."
 * The first one is always free.
 * And tea = alcohol.
 * Imagine "Cake, Hugs and Rock 'n' Roll" as a marketing slogan for K-ON!.
 * Hey, if you replace the word "cake" with the word "drugs" in that, it kinda rhymes!

Summary: Yui=Subaru and Ui=Ginga.
According to various WMGs here, the girls are expies from Magical Girl Lyrical Nanoha, and they look like twins despite not having the same age. So, the answer is obvious: Yui, the clumsy book-dumb who can do anything when she actually tries, is Subaru, while Yamato Nadeshiko Ui is Ginga. Since they're clones, they're basically twins with an age difference. And yes, Ui is the older sister—it's been officially decided by the Club President in episode 8.

Strike Witches is what happens when the opening theme is taken to its logical conclusion.
If they cut their skirts by a couple centimeters, they could jump higher than they could before.

So if they remove the skirt altogether...

K-On! is an alternate story of how Estonia's Urban Symphony was formed.
Manga was released in 2007. Band formed 2007. Anime released in 2009. Band participated in the Eurovision of the same year. Check out the band too: Mio has a very convincing IRL equivalent.
 * Second from right even has Mugi's FACE.
 * Is this a confirmation of Mugi's Finnish roots? Note that Finns and Estonians are related ethnic-groups.
 * ...they all have the kind of faces I'd picture the girls to have IRL: L-R is like: Ritsu, Mio, Mugi and Yui.
 * Can they be the IRL!K-On versions of Apocalyptica?
 * I think I can live with that.

They're all GenderFlipped Doppelgangers of the Beatles.
Ritsu is John, Mio is Paul, Yui is Ringo, Mugi is George, Azusa is George Martin (the Beatles' producer; occasionally called "the fifth Beatle"), and Sawako is Brian Epstein (their manager).
 * But Ritsu plays the drums! ...I suppose little details like that don't matter. Yep, it's like the points from Whose Line Is It Anyway?
 * In this case, it's the personalities that match up rather than the instruments. If God really is Haruhi, she might think it fun to mess with our minds and switch the instruments as well as the genders.
 * So if Ritsu suddenly gets a boyfriend, then it'll be the end of the band?
 * Yep. Especially if Mio has a thing for Ritsu. Ritsu should also beware of disturbed fans who also like The Catcher in The Rye...
 * Probably Mio will finally realize her song lyrics are awkward, so she'll hire a lyricist who ends up as Ritsu's boyfriend and brings up the end of the band.
 * I'll have a different take on this. Agree with who Mugi, Azusa and Sawako are supposed to be. But, Ritsu is Ringo, Mio is John and Yui is Paul. Granted, Yui hasn't written any really good songs (yet). But, still...
 * Bonus points for Mio being a left-handed bassist.

K-On! takes place in the same universe as So Ra No Wo To.

 * For all we know, the K-On cast are the Identical Grandson descendents of the So Ra No Wo To girls.
 * Which would kinda explain how the animation style and the characters' designs are virtually alike.

The girls make it big later on and write the opening and ending themes.
Those songs don't appear in the show, and the Ending Theme, "Don't Say Lazy", especially is different from their other songs in style and in the professionalism of the music video.
 * That is, if a boy doesn't come between them first.
 * Does this mean the entire show is really a Flash Back?
 * Sure, why not? We're seeing fond memories of their early career, before Mugi was shot by a broke dope fiend.

Ritsu is a "Svengali" for Mio
She consistently "programs" Mio to be shy, in a jealous or selfish effort to keep her relatively friendless or dependent on Ritsu.

Flashbacks suggest that her badgering of Mio began from the moment Ritsu first met her. She may be smarter (or more sinister) than she lets on.

The class trip to Kyoto takes place on the same days as the Konata's class trip! They just never crossed paths!

 * Where did the idea for this one come from?
 * They both went on trips to Kyoto as a class, in a universe very similar to each other, in a shows that aired two or three years apart.

Ui is an Alternate Universe version of Persona 3 Portable's Female Protagonist.
All the proof you need.
 * Woah.
 * This troper thought he's the only who one noticed the resemblance...

Mio is an Alternate Universe version of Persona 4's Yukiko Amagi.

 * I mean just look at the AMV when the Persona 4 girls replace the band for the ending song.

Mugi is only part Japanese.
You Gotta Have Blue Hair is mostly averted in K-On, with the exception of blonde Mugi (blonde hair is, of course, pretty rare in Japan). In the first Beach Episode there's a brief shot of Mugi as a little kid with her parents on the wall of her beach house (the facial features are a bit too blurry to make out, but you can still make out her hair). So the hair isn't a dye job. Perhaps her dad studied in America or Europe and married a classmate. Or perhaps her mom is Finnish and studied in Japan (it might explain their apparent villas in Finland).
 * This actually kind of makes sense, but we need moar Epileptic Trees.
 * Okay, how 'bout this... She speaks not only fluent English, but also Finnish, and some Swedish (Finland was once ruled by Sweden, and Swedish is still spoken in parts of the country).
 * But can Mugi be both a Hafu and a natural blonde? I was under the impression that blondeness wasn't dominant, and any Japanese-European pairings would yield black-haired kids.
 * Phenotype Stereotype. By the laws of anime, even partial Japanese heritage will result in blondeness if a parent is white. Even if not all white people are blondes in the real world or in the show. It's only averted with realistic representations, such as Death Note, etc.
 * Definitely more believable than the theory that Miyuki is a hafu.
 * Sumire from K-On! High School only complicates things. Another blue-eyed blonde, she's the daughter of two Kotobuki family servants and Mugi's unofficial "little sister" -- and despite her Japanese name she's ethnically Anglo-Australian.  Which no one in the club realizes until she tells them.

The girls are all in an alternate and ultimately happy universe!
Just think about it. They're all happy, can easily get jobs, and have no problem with their lives. Hell, if they turned out to be all lesbians, they'd probably face no opposition! In fact, the possibility of them in the real world is Deconstructed by the Doujin Requiem 5 A Dream. It all makes sense!

The girls are a fantasy of Haruhi Suzumiya!
Just...think about it. Haruhi said once to Kyon We can be idols...with instruments!. Since Kyon thinks that the idea sucks, Haruhi created the girls of K-ON! And that's why the girls are alike the characters of Haruhi Suzumiya. Forgive me for my English!

Sawako from Kimi ni Todoke is actually Mio in a parallel universe where she never met Ritsu.
In a world where she never has a friend to help take away her shyness, she never gets in to music and ends up going to a different high school altogether.
 * Also, Sawako's mom bears a striking resemblance to Yui Hirasawa. Perhaps this is in the future, when Yui gets married and she names her daughter "Sawako" after her favorite teacher.

Ui is older than Yui.
According to the DVD box set, Yui's birthday is November 27, and Ui's is February 22. This would make Yui three months older than Ui, which is clearly impossible. Therefore...

Ui is actually the eldest daughter, while Yui is the youngest, making Ui older than Yui by about nine months; thus, they should have been in the same class. However, because of their parents' prolonged absence, Ui was forced by her sense of responsibility to take care of her younger sister, and was held back a year in primary school as a consequence of not being able to focus on her schoolwork. Also, being young when their parents left them, they forgot who was the eldest, and they assumed Yui was the eldest because she was one year ahead of Ui in school.

It makes sense, especially if you consider the two girls' behavior: Ui is almost the stereotypical older sister, taking care of her younger sister, while Yui is the younger sister lazing under her older sister's care.


 * Why not just say that Yui is 15 months older than Ui?
 * Because if she was she would be two years ahead of Ui in school, but she's just one year ahead.
 * Don't know how the Japanese school system works, but if Ui was still born in the year after Yui, wouldn't she still only be one school year behind, even if there's an age difference of more than 12 months? There's a 19-month age difference between two of my cousins, but the younger was only one school year behind the elder.
 * This depends on exactly how the Japanese school system works. For example, in Italy, everyone born from January 1 to December 31 of "year 1" is lumped together in a class, while those born from January 1 to December 31 of "year 2" have to wait for the next school year to enroll, even if they are, in a worst-case scenario, only a couple of minutes younger than the students who started school a year before them. Assuming the system is alike, it's possible that a different "cut-off date" was chosen: if Yui is 15 months older than Ui, the situation would be as it is in the anime (Ui one year behind Yui) if the cutoff date is anywhere between February 23 (one day after Ui's birthday) and November 26 (one day before Yui's birthday).
 * It is probably more likely that Yui is the one who got held back a year, making her one year ahead of Ui instead of two.
 * The drawback to this is the question of when Yui was held back a year, because the flashbacks show that Yui and Nodoka have been in the same classes together since kindergarten.
 * Yui could have entered kindergarten a year late. One possible reason could be that she came down with some dangerous illness or injury in the year when she was supposed to enter, and thus had to spend several months in a hospital instead. Another could be that her local public kindergarten had a ridiculously long waiting list while her parents could not afford to send her to a private one (this is a very widespread problem in my country, but I have no idea how it is in Japan).
 * IIRC, anyone born before the start of the new school year in Japan goes to school with those born in the year before them, so in other words, people born from April 1 to March 31 are all in the same school year. This makes Yui and Ui being 15 months apart in age and one year apart in school understandable.
 * The above makes the most sense, as This Troper was born in September and is one of the oldest students in his class. Yui was probably not "Held back" in any part of school, she would have simply started school later then usual. Ui being the oldest would make even less sense, since Yui is a grade ahead, which would've required Ui to skip 2 years. Plus, it's entirely unlikely that their Mother would have given birth 9 months after her first pregnancy, there's a lot of health complications related to back to back pregnancy like that, especially the conception part. Yui is older by 15 months.
 * with her parents being trabel agents, she being the first born and the fact that the most parents cant let alone their first kids due the frigth and lack of experience. what if Yui parents just made Yui loss a school year by taking her to travel with them?
 * Even if the parents could have forgotten who was the eldest, Ui definitely could not, and yet she always refers to Yui as "Onee-chan". Sure, Ui could have agreed to play along and pretend to be the younger sister for the rest of her life, except in the Christmas flashback (season 1, episode 7) it is shown that she called Yui "Onee-chan" even when they were both pre-schoolers.
 * All that proves is that Ui's viewpoint isn't objective.

Sawako's musical inspiration is Zakk Wylde.
The Ozzy Osbourne music book, her Flying V guitar and metal style...it all adds up!
 * In season 2 episode 10, when Sawako's bandmate Norimi recruits Yui to substitute for Sawako in a Death Devil performance, Norimi modifies Giita to look like a Zakk Wylde custom Les Paul, complete with the bullseye decals on the body. This also relates to the next WMG...

Yui displayed Obfuscating Stupidity at the wedding performance.
All the members of Death Devil and HTT planned in advance to have Yui deliberately play the song badly
 * It's a sad thing that this had to be put in WMG instead being automatically Canon.
 * I thought that was what was really going on...

Death Devil's bassist "Della" is Himeko Tachibana's older sister.
They'd have to be separated in age by ten years, though. See here.

Sawako is a fan of Bubblegum Crisis.
The B-side of Death Devil's "Love" single is called "GENOM". This is likely to be a Shout-Out to the fact that Yuu Asakawa, who plays Norimi and sings backing vocals on this album, previously played Priss in Bubblegum Crisis: Tokyo 2040 but didn't do her own singing. Death Devil is a way cooler band than Sekiria, anyway.

Yui is a certifiable genius and her ditzy side is simply very masterful acting.
We already know that Yui's got natural talent for learning, so it's not impossible that she's just all-around brilliant. She's got the motive, too- Ui does all her work, feeds her, and lets her do whatever she wants, she can practically get away with murder at school, the other club members will do lots of things for her (such as Azusa tuning her guitar), and when she DOES manage to do something, everyone is more impressed than they would be if she showed her brilliance all the time. It's not unheard of in real life for a smart kid to feign idiocy to such ends.
 * Brilliant but Lazy, in other words?
 * Sounds more like Ditzy Genius to this troper.
 * More like Brilliant but Lazy combined with Obfuscating Stupidity to me. Brilliantly Lazy?
 * She probably just has a mild form of ADHD. It's also heavily implied that she suffers from a personality disorder of hyperfocusing. Where one completely dedicates themselves to a particular task and totally fall apart in other areas.

Aya Hirano will guest star on K-On!!.
"In fulfillment of the awesomeness!"

Tsumugi is an Android
Think about it: She has freakish super strength, fascinated by the ordinary and mundane things and life, anyone in the Kotobuki Consortium knows about her, and. She was probably commissioned to be built by the President out of grief after his real daughter died in childhood. The Company probably anticipated her completion when the real Tsumugi would have entered high school (and thus built her body as a high school girl), but programmed her as if she were still a ten-year-old. She also needs annual maintenance in Finland.
 * She also has extreme concentrating skills, as seen during the car-counting.
 * Well, except that she mistakenly pressed the button in response to Yui asking her something.

K-ON! is an Alternate Universe of Strike Witches
Think about it: The characters main characters look very similar to each other, and the differences can be ascribed to the fact that they were free in one 'verse and forced to fight for their lives in another. Mio is most obvious, as she had to get tough instead of adorable. The fact that they still share a name helps. Oh, and she gets a Geass, fulfilling the "otherworldliness". Yui is, of course, Yoshika. She stays the (relative) main character. Erica and Ursula Hartmann are the alternate-universe twins for the Strike Witches 'verse, replacing Yui and Ui. Mugi is, over course, Eila Ilmatar Juutilainen. They are both connected to Finland Suomos, with Mugi's family owning a home there. In another world, they could have lived there permanently (or maybe Mugi's blondeness is due to her being But Not Too Foreign?). I can't be sure about Ritsu... maybe Charlotte E. Yeager? They have similar hair color, and then there's the more confident and loud attitude... As for the lack of pants in Strike Witches... well, I can't be th only one who figures that it would be right up their alley for these girls...
 * Semi-supported due to one line in the opening theme: "If we could shorten our skirts a few inches, we could fly". Taken to its logical extreme (remove the skirts entirely), you get the characters from Strike Witches' main complaint: "They're not panties!"

Yui will become Yui Ikari
Yui, upon graduating, leaves Hokago Teatime. She then leaves for college and eventually becomes a respected scientist/roboticist. She marries and has a son. She names him...Shinji.

Oh Crap, Gendo's wife and the lead guitarist from K-On! are the same person! No, this doesn't make any sense. At all. But it is hilarious to see what would happen if you mixed a Tastes Like Diabetes Slice of Life anime from Kyo Ani with a deeply disturbing, super-Mind Screw anime from Gainax.

And yet...it makes sense, in its own twisted way. Yui Ikari, from what little we know of her, is/was kind and caring, most likely the kind of person Yui Hirasawa would be when she grows up, if her Sickeningly Sweetheart parents are any indication. Plus, as it says on the character sheet for NGE, one of the Evangelion games states that Yui Ikari was the daughter of a SEELE member, but the canonicity of the game is debated. If it were true, though, this could possibly explain where Yui's parents are going for all their "vacations". Or not.

Please don't flame me.


 * Don't worry man, it actually can make sense, if Yui Ikari's parents information is put into canon then when she grew up and begin to work in Gehirn maybe, under SEELE's orders, Yui had to change her family name to Ikari instead of Hirasawa for the safety of Project E, and everyone knows that in EVA's universe the technology is more advanced then this universe, so K-On! can take at least around 1990's or earlier in EVA's universe.
 * Hey, Ikari is Gendo's family name. Yui Ikari's maiden name could've been Hirasawa. Whoa... Did Yui Ikari ever show any musical ability?
 * Wrong. Ikari is Yui's family name. Gendo's is Rokubungi. Gendo took Yui's name because it was more prestigious, Fuyutsuki even notes the oddness of him doing it. There really isn't enough evidence to come to this conclusion. Plus...Yui H. doesn't really seem dedicated enough to be a student majoring in genetic engineering at Kyoto U.
 * Maybe she could have matured when she entered the university
 * Or she followed Nodoka-chan to Kyoto University once she graduated. After that, Nodoka introduced Yui to her cousin, Rokubungi Gendo.
 * I also think that there is conspiracy between KyoAni and Kakifly with Hideaki Anno and Gainax. I don't think that the reason that both have used covers of Tsubasa wo Kudasai and the difference between the premiere of Evangelion 2.0 and the airing of K-On! were just 2 months were just concidences, in fact I think that's part of the conspiracy. When "Tsubasa wo Kudasai" starts be played in the background in 2.0, I think that was lampshading of Yui's past, because "Tsubasa wo Kudasai" was the same song that was both the first song that Yui listen from Ritsu, Mio and Tsumugi and the song made her decide to stay in the light music club thing that helped her to mature, and as I said above, she fully matured in the university and when she graduated she started to working in Gehirn and you know the rest.
 * This is of course Jossed regardless of the silliness, as recent chapters (and in the past week as of this entry, the anime) show that all four girls were accepted into the same college.
 * Yeah, you're right, and with the introduction of Yui's parents is now very obvious that her parents can not be SEELE's members. But at least it can still be in the same timeline as NGE, in a parallel timeline that I create with three different WMGs that I named: The "KESCG" Anno Domini.
 * Perhaps Yui's daughter inherits the "smart genes" carried by Ui in this generation. She then carries them on to her daughter...and so it begins. So Shinji is Yui Hirasawa's great-grandson.
 * I like this much better and now it makes a little more sense, but, this also means that K-On! takes place before World War II and let the possibility that Ritsuko could be the granddaughter of Ritsu.

The entire series is a Where Are They Now? Epilogue about the childhood friends of Chiyo-Chan.
Look at both shows time-wise in accordance to the last Azumangas air date (2002) and K-ON's first (2007'), and you'll see that they are roughly five years apart, just old enough for all of Chiyo Chan's childhood friends from grade school to have gone into high school. In this sense, it's no wonder so many characters share the exact same traits as several characters on Azumanga (ie, Mio and Ritsu are obviously Yomi and Tomo, Tsumugi has a shy disposition like Sakaki, Azusa's a Child Prodigy like Chiyo-chan, and Yui is very, very akin to Osaka). Chiyo-chan probably introduced them all to her friends! Plus, I'm going to go out on a limb here and say that Sawako and Yukari are probably very friendly teaching associates.
 * I wonder if the teacher Kimura-sensei talked with was from Sakuragaoka...
 * I suppose Sawako Yamanaka is similar to Yukari Tanizaki.

The girls' first two years of high school were either dull and boring, or depressing and traumatic.
But the series can only show the happy moments of their high school careers, and none of the drama. Thus two years of high school were compressed into 14 very slow-paced episodes while in most anime this would only be enough screen time for one year. Itoshiki-sensei would agree.
 * Apparently, it got better in their Senior year.
 * Based on the episodes we saw in the first season, their first two years were depressing and traumatic... for Mio.

The original four band members are the byproduct of Kyon's polygamy.

 * Being a well established Mormon, Kyon is married to the other Bridget members and fathered the light music club's original members. Being that polygamy is one of the few socially unacceptable types of relationships in Japan, Kyon and the Bridget kept it quiet.
 * Kyon and Mikuru had Yui, Kyon and Yuki had Mio, Kyon and Haruhi had Ritsu, and Kyon and Koizumi had Tsumugi.
 * I almost lolwut'd on the last one, then I remembered that it is Haruhi we're dealing with... which raises the question: was it Mpreg, or did Haruhi turn Koizumi into his gender-flipped counterpart?
 * This is absurd, Mormons are against homosexuality, since Kyon had Koizumi had a child together Kyon cannot by Mormon.
 * Made even more absurd by the fact that the Mormons don't practice polygamy anymore.
 * Mugi could be Kyon and Asakura's child, which would explain the eyebrows.

Yui is truly in love with Azusa
Come one, how much more obvious does it have to get? She is quite clumsy in showing her affection, though, fueled by her inexperience and ditziness. Azusa might realize something is up as well, which leads her weary responses during their sleepover at the school. Maybe Azusa thinks that Yui, as a sempai, should take the initiative.
 * Tooootally done on purpose.

"Utauyo Miracle" will be the final concert that will end the series
At the time of writing this WMG, there are six more episodes in the anime, and one more chapter in the manga to go. Obviously, the four seniors will graduate...and they will do so with a bang! A final concert in Class 3-2 (can't use the auditorium since it's being used for the ceremony) is a fitting way to end their time in High School.
 * Confirmed! But we had to wait for the movie for it to be shown.

Nozomu Itoshiki will be transfer to JWU.
Hey it is called Wild Mass Guessing, right? As a result from his incredibly successful teaching methods, Ms. Chie convinces forcibly recommends Nozomu to transfer Japan's Women's University, an all women's oriented university. Even worse for him is that as a new teacher, the university's guidance counselor force him to help oversee a newly formed club, called the Light Music Club II, as their new club's advisor.
 * Somebody please write a doujin about this immediately!!

The girls of K-On! are Gender Flip versions of U2, in a Slice of Life fanfic.
Said fanfic is written by the girls of Lucky Star. Though the girls don't correspond to the musicians with the same instruments, like the Beatles WMG, it doesn't matter as much, because Konata willed it. Ritsu is Bono (Genki Girl, Large Ham), Yui is Edge (Cloudcuckoolander guitarist), Mio is Larry (Shrinking Violet) and Tsumugi is Adam (posh, English, blonde, quiet). Ui is Dik Evans, Azusa is Danny Lanois, Nodoka is Gavin Friday and Sawako is Brian Eno.

Ui is (or at least used to be) The Unfavourite.
Yui's name is written with the kanji 唯 ("only"), implying that the Hirasawa parents did not want more than one child. Ui's name is written with the kanji 憂 ("grief" or "melancholy" - just like in 涼宮ハルヒの憂鬱 or Haruhi Suzumiya), which may be an indication of how the parents reacted to the birth of an unplanned second child. The reason why Yui is so lazy and immature is that their parents doted on her, while making Ui do the household chores. However, they managed to do this without outright abuse, which is why Ui became responsible and caring, rather than resentful and envious (the fact that Yui herself was very nice to her, as seen in the Christmas flashback, must have helped as well). They probably learned to accept and love their younger daughter eventually, after seeing that she had become an indispensable part of the family.
 * OP here: after having learned Japanese a little more I see that my kanji interpretations were a little off - 唯 means "only" not as in "the only one", but as in "simply", "merely", or "just", and it also has another meaning of "ordinary" or "usual"; 憂 can also mean something like "considerate" or "sympathetic". However, at least one work does explore the idea of Ui being The Unfavourite...

Yui is Sonsaku Hakufu from Ikki Tousen
Goei has, at last, found a new husband, and has decided to travel with him. So, she left her daughter Hakufu under the care of her Yamato Nadeshiko younger sister Chuubou, with an ultimatum: don't rip your clothes, don't damage the house, or you'll see hell when I come back!

So, Hakufu gives up on fighting, and takes up guitar instead. Just like she managed to copy martial arts without knowing their names or the theory, she learns guitar without a clue about musical notation. And she tunes her guitar by ear, just because she didn't know about tuners. Perfect Genius Ditz as always!

Overall, she hasn't changed much: she's still a Nice Girl, always cheerful and friendly to everyone. She has a one-track mind; her motto is "Don't think too much, just be yourself and have fun". She's still a Big Eater; and she doesn't mind wearing cosplay outfits.

Since she's extremely Book Dumb, you might wonder how she got (and stayed) into a good school like that. Quite simple: her smart dragon wakes up from time to time, and answers the tests in her stead. Hence her surprise when she sees the resulting near-perfect grades!

She couldn't forget about Ton-chan though, so she named the tortoise like him.

The final episode will be a flash forward.
To when the girls are adults.
 * Nope. It turns out to be the real last episode of the show, instead of an extra one.
 * It's not really the last episode, anyway, since a movie is on the works.
 * It's the last bit of K-On! made for television, so yes, it is the last episode. Still nothing is known about the movie anyway—it could be a simple rehash of the TV series, as far as we know. Since pretty much all of the manga has been used for TV, it's either that or something completely new.
 * Jossed: the OAVs and the movie are all set during the TV series, not after it, so the final TV episode really is the last episode.
 * The manga, on the other hand, picked back up with two parallel storylines -- Mugi, Yui, Ritsu and Mio in college together (K-On! College) and Azusa forming her own band in her senior year at Sakuragaoka (K-On! High School).

Tsumugi is a Time Lady.
It's right there in the theme!

The girls of K-On! are Gender Flip versions of Restart, but slightly tweaked.
Yui is Pe Lu with Pe Lanza's carefree persona and hair color, Mio is Pe Lanza with Pe Lu's responsible persona and hair color, Azusa is Koba, and Ritsu and Tsumugi are both Thomas. Not only that, but both bands play the same kind of music: Restart's happy rock is essentially "light rock".

Plus, compare the first few seconds of "Breve História" to the first few seconds of "Fuwa Fuwa Time".

Alternatively, the band Azusa may form after the finale probably will parallel Restart.
While Azusa will upgrade into being Pe Lu's counterpart, her previous position as Koba's counterpart will be filled by Ui, while Jun may become Pe Lanza's counterpart, and Thomas's counterpart might be very well a New Transfer Student.
 * This theory is strengthened by the fact that Sumire, the new drummer, is blonde, thus making her the "Thomas" the band was lacking.

Yui gets employed as a roboticist for the Buy N Large Mega Corp.
Similar to the robotics one above. In college, Yui becomes an electrical engineer in robotics, she finds a new job at a newly formed company called Buy Yogurt, which she joins instantly after being given free samples. Later on, Buy Yogurt acquires a clothing company called Large Industries, and the company renames itself Buy n Large. The company becomes a huge success in mass conglomerate goods and start selling everything, including robots. Yui eventually transfers to their robotics division, where she begins to design the world's first Waste Allocation Load Lifter- Earth class robot (although not needed for another 50 years).
 * So...is the Crapsack World that Earth becomes in WALL-E actually Earth after the Third Impact?
 * Yes. Every wondered why WALL-E, M-O, Auto and EVE looked so cute? Bingo.

Sawako is actually a future version of Yui sent back in time to stop some cataclysmic event.
That's right, Sawako (future Yui) comes from a crapsack future where the only way to save humanity is to go back in time to prevent some key event from happening. With her knowledge of the past, Yui goes back with a fake teaching degree, back story, and name to meet her old self and use her to stop said event from happening. If you look at the few pictures of Yui's mother in the manga, she is almost completely identical to Sawako. Much like some women look like their mother if you compare photos of them at the same age.

Yui and Ui went to France and Italy when they were little kids.
Their parents were pretty much out of the country for much of the series (at least as far as we can tell), so it wouldn't be a stretch of an imagination that the sisters went with their parents overseas as toddlers. Why else would if they're not gonna use it?

Evidence to support this include Yui's love of food (and craving a Marinara Pasta during the Summer Music Festival), and Ui's Character Image song "Oui! Ai Kotoba". It's just too bad most Japanese schools prefer to teach English as the requisite foreign language instead of French.

Azusa will go to the same university as the other girls after she graduates.

 * Isn't that a foregone conclusion?
 * Which? Nodoka aims to go to K University, Tsumugi's decided on N Women's College, Mio's going for recommendations, and Ritsu's undecided. (Which wasn't okay, but we still don't know as of the end of volume 3.) If they drift out of the focus of the series (or it ends before it would have a chance to follow them anywhere), then it won't really matter that much that they're separate. Hey, even the primary main girls of Lucky Star have mostly gone to different schools, and that series hasn't ended. So I'd consider it merely possible.
 * According to K-On! College Yui, Ritsu, Mio and Mugi all ended up at the same school, where they are continuing to perform as HTT. That makes it pretty easy for Azusa to pick a college when her time comes.

What's the relationship between Mugi and Sumire?
Sumire Saitou, one of the two first-year students who joins Azusa's Light Music Club in the restarted manga's high school storyline, says she lives at the Kotobuki household and calls Mugi "Tsumugi-ojousama". From this we can speculate, in order of increasing tenuousness:


 * 1) Sumire is the daughter of Mugi's butler. The butler's name was established to be Saitou earlier in the manga.
 * 2) Mugi is pulling a Batman Gambit to get Sumire to join the Light Music Club. She probably ordered Sumire to bring back the tea set in the hopes that Azusa, Ui and Jun would meet her and recruit her into their band.
 * 3) * Semi-confirmed in Chapter 62. Mugi left her tea-set intentionally so Sumire would visit the Light Music Club, and make friends there. Joining the club was an added bonus.
 * 4) Sumire is Mugi's half-sister. We know Mugi inherited her eyebrows from her father, so did she get her blonde hair from her mother, who is believed to be Finnish? And Sumire looks very much like Mugi except for the eyebrows. The problem with this theory is, if the lady of the house had an affair with the butler, how could the butler not have gotten fired over it?
 * 5) * Perhaps, Mugi's parents have an open relationship.
 * 6) Mugi is her (non-related?) Cool Big Sis.
 * 7) * Confirmed in chapter 62. Although the Saitou family has traditionally served the Kotobuki family, Sumire treated Mugi as her big sister, until her family's role was revealed once she hit twelve. Although Sumire refers to Mugi as 'ojou-sama' at school, she still apparently calls her 'onee-chan' at home.

The movie will be about their foreign trip.
Come on, it would be dumb for them to have an entire episode about preparing for a trip an yet they never go.
 * Confirmed; the film is about their trip to London.

She's pretty much has Nodoka's looks mixed in with Yui's personality. Came back in time to save Azu-nyan to prevent. But her mission was jossed and rendered unnecessary since her mere presence caused.

Mugi is a Sexual Deviant with Magical Tea.
This is just a crack theory, but I thought I'd share it.

It's been shown that Mugi wants two things: to get hit, though it was played as her wanting the skinship she damn well deserves and that she doesn't like when people fight, so she offers them her magical tea and cake. And this all started in her childhood...


 * When Mugi was a child, her parents fought a lot. Sometimes the arguments would be so heated that her parents would hit each other. Mugi, being as kind as she is, would sometimes take the hits for either of her parents. Sometimes during the hits, she'd be scolded by her parents. This went on from the time she was 3 until about 13. Somewhere within this time, most likely when she became aware of her own sexuality, the physical blows went from "painful" to "this is my fetish". Unfortunately (for her), her parents went to family counseling and their relationship was fixed. No more hitting. She craves scolding, hugs, and slaps for her sexual pleasure.
 * As for her tea, this also stemmed from when her parents fought. To get them to stop fighting, she developed a special tea that could calm even the most savage of people with one sip. The main ingredient was alcoholic in nature, though it was mixed with things like lavender and chamomile. Haven't you noticed that, even in the show, Mugi offers her tea whenever anyone is distressed, sad, angry, or arguing? And when they take it, that stuff usually stops? Exactly. She usually offers cake with her tea because it sweetens the deal.
 * And there was also that episode in season 2 when Sawako wanted tea and sweets but they couldn't use the music room during Finals. It's not that Sawako wanted sweets, she was addicted to the alcohol in the tea! It'd explain why she was basically having tea withdrawals.

Yui and Ui went to the same middle school as Kagome Higurashi.
Same uniform design. Of course, Inuyasha came out over a decade before K-On!, so they couldn't possibly have been classmates with Kagome... (or did they?)

Mio is afraid of barnacles because...
...She heard the story of The Ugly Barnacle and was scarred for life.
 * This had to be done sooner or later.

After the last of the four or five finish college, the girls will become a professional band.
First order of business? Teach Yui basic chords... again.

Side character Fumie Kimura is a twin or a triplet.
The Namayake girl standing next to Fumie in this picture resembles her quite a bit. Another background girl, shown in this picture looks like she could be related to both girls as well. Perhaps one of them is Fumie's twin sister or both of them are her sisters. Or Kyo Ani felt like being lazy with character designs when producing the episode. Since we don't know much about Fumie.... it could be true

Background character WMG
This girl is Kyon's sister in an AU of Haruhi Suzumiya They do look alike.

Class 3-2 student Kimiko Makigami is only half Japanese
She clearly has a darker skin tone, at least compared to her classmates. Perhaps she is biracial. Some netizens have dubbed her the "foreign looking" girl in class 3-2.

Yui and Ui are part of a nefarious cloning experiment
Specifically, they are an experiment to recreate Sherlock and Mycroft Holmes. Their "parents" are actually handlers in charge of training them to follow in their male predecessors' steps. Ui is Sherlock (a balance of single-minded brilliance and functional skills) while Yui is Mycroft (maybe a bit more skilled when it comes to single-minded brilliance, but otherwise lethargic and less functional.) The experiment more or less failed however when, instead of discovering the joys of investigation/secretive operations, they discovered the joy of music.

Mio and Akemi Homura are orphaned twins Separated at Birth.
We never see Mio's parents, so she could possibly be adopted. The sorrow of not knowing her birth parents may have contributed to her initial Shrinking Violet nature.

Sayaka Miki is Ritsu's cousin.
Let's assume that in the Madoka-verse, turquoise hair is equivalent to Ritsu's light brown.

Mami Tomoe is Mugi's cousin.
Both their mothers were Finnish sisters who attended the same Japanese university and fell in love with two certain Japanese men. The lingering racial stigma of being "hafus" made both girls quiet, isolated and lonely.
 * Hitomi Shizuki (aka "Green Mugi") is another cousin of Mugi's, on her father's side.

Sawako Yamanaka is the daughter of Takano Miyo
Sawako youthful age would place her being born around the early 1980's, which coincide with the events of Higurashi no Naku Koro ni. Both Sawako and Takano share the similar hair styles, facial features, beauty, and the occasional bout of insanity. Sawako glasses and dark hair, in contrast to Takano, can be explained as traits of her father, Tomitake Jirou. Both Sawa-chan and Miyo also share the same voice actress in the dub.

The ending songs of both seasons and the movie are those of the girls after making it big
This would explain why they are done as an actual music video and Mio is the lead singer because her voice is more mainstream compared to Yui's and/or she overcame her shyness.

Yui and Ui had their personalities switched when they were too young to remember.
Why else would the little sister be more mature?

Sawako is not right in the head.
Because no one can be like Sawako and be mentally stable.

The first ending is a music video from the future
As noted above, they appear older (though not significantly), and Mio seems confident. Presumably after being together for a few years, Mio is able to work through her anxiety through some means and is able to become the lead singer. Yui is happy to become the backup vocalist, and because of the change in voice types, their sound becomes much more mature than before (in the first opening and during the series).

Are Ritsu, Yui and Mio a ComicTrio?
Ritsu is the self-claimed leader. Mio is obviously the complainer. Yui is the one who keeps things going, and is also the most easy to manipulate. Sawa-chan, Azusa and maybe Mugi could fill respectively similar roles too, although with different results... Or not.

Tsumugi is a descendant of the Engineer from Team Fortress 2
If the official comics and other Team Fortress 2 lore are to be believed, Tsumugi has a lot in common with the Engineer. The Engineer had blond hair and blue eyes (there actually is a cosmetic item called the "Big Country" that is the Engineer's hair as it was before he shaved it off, and he is shown to have blue eyes in a couple of the comics.) as well as considerable upper body strength (Engineer can carry those big toolboxes his buildings are in, and Tsumugi is shown effortlessly carrying heavy band equipment). Also, the Golden Wrench could explain how the Kotobuki family became so wealthy.

The whole series is Yui's dream
Yui, being in a huge hurry, gets hit by a car in the beginning of the first season, and then goes into a deep coma, in which she dreams about a happy-go-lucky life with lots of cool friends which are based on the cool girls she saw when she ran passed them (Mugi, Ritsu and Mio can clearly be seen in the first scenes). Notice that there is an odd gap between the street Yui is in and the school she eventually reaches. In reality, that school is even in a totally different town, but in Yui's dream it's nearby, as she might have thought that the school in Toyosato looked so cool (or maybe she even attended the elementary school next to it). It all does explain why everything goes so smoothly most of the time, and how Yui could learn to play the guitar at such a level so quickly—it's simply something she wished to be able to do in real life.

Azusa had a lonely childhood
In (S2) episode 5 where the band had matching keychains that spell "keionbu" (to symbolize their friendship), Azusa hesitated to 'complete the word' with her own keychain that they gave her. This is probably because she's not used to having people consider her as a "friend". She had no close friends in the past, maybe because she had an arrogant personality (it's shown when she daydreamed about being the club president). The other kids disliked her and this led her to have low self-esteem and become more serious. It's why Azusa begged the other girls under tears to not graduate. She didn't want to lose her only friends and become lonely again.

Mio and Ritsu are in love with each other but don't know that the other one feels the same way.
Mio is probably just too shy to say anything (even if it is Ritsu something like that would be hard for Mio to say). Ritsu probably hasn't figured out her own feelings yet (Ritsu would definitely say something once she figured it out).

Yui doesn't care if something is male, female, or an inanimate object as long as she thinks it's cute
The two things she is most fond of are Gitah (a guitar that she seems to think of as male, cute and her boyfriend) and Azu-Nyan (a very cute girl), so her current love interests cover all three categories.

Yui is actually Lain Iwakura.
After erasing herself from everybody's memory and realizing her true nature as the goddess of the Wired, Lain eventually decided she wanted to live like a normal girl again, only with a life full of happiness instead of the seriously depressing one she used to have. She then created a new world inside the Wired where she lived as a childish, optimistic high school girl who sang and played guitar in her school's light music club. Note how both have brown hair (okay, Lain's is darker than Yui's, but whatever), have similar hairclips, play the guitar, and have a knack for becoming geniuses at anything as long as they have the motivation to do so (guitar for Yui, computers for Lain).

Sawako is secretly related to the principal of Sakuragoka.
Because be honest; would you hire someone like her on normal circumstances?
 * Yes i would. she seems to be a competent teacher, she acts like a teacher should most of the time (the series focuses more on Sawako acting like herself but shows enough of her acting professionally to establish that she is good at it and that it is her normal behavior) and all of her students love her.

Mugi is Satsuki Kiryuin's distant relative.
Eyebrows.
 * Wealth.

Ui has a primitive proto-version of the sharingan
That's how she learned to play guitar: She watched Yui play it and copied and assimilated the finger movements.
 * That isn't all she copied - she learned ventriloquism from a book and put on a convincing show in the same week, she can impersonate her sister (who she's spent a lifetime observing) with such perfection that her sister's closest friends didn't figure it out until Ui slipped up on one girl's nickname, and after overhearing a short description of how to swing a baseball bat she was able to hit a "home run" sign at a batting arcade and win a prize. And the Marvel Cinematic Universe version of Taskmaster is female... Is Ui fated to become a supervillain?

WMG: Mugi is the Yuri fan-tendencies in animé/manga fans personified
Just look at the YMMV or Ho Yay subpages on this site or the Yuri-forum on 4chan and you see people jamming Yuri in a whole lot of things just as Mugi does.

Mugi is A-ko and C-ko's daughter
She gets "blonde" and "slightly ditzy" from C-ko, and "incredibly strong" from A-ko. We never get to see her family because having two mommies was still socially unacceptable in Japan when K-On! was made. As for the question of how two females could produce a child on their own, consider who A-ko's parents are; comic-book biology trumps real-life biology.

Sawako is trying to sabotage the Light Music Club
She was blackmailed into becoming the club advisor, after all -- why wouldn't she want to get her freedom from the responsibility of advising a second music club? Hence the ridiculous costumes she keeps trying to get the girls to wear, and the halfhearted band names that she forces onto the bands. If she can get them to dissolve on their own, it won't be her fault that she goes back to her old life.