Sayonara, Zetsubou-sensei/WMG

After 'The House Of The Girl With Glasses', Itoshiki-sensei can cheer up.
His despair-inducing squeezing glasses were stolen by ghosts when he forgot to write sutras on them; he should be able to think positive thoughts now.
 * Nope. Now He'll just despair about not having glasses.

Kafuka writes the series.
To wit: Mostof the more normal stories — Itoshiki-sensei's trips into town with the girls to find things to despair about; most of the classroom stuff — actually happened, while the more surrealistic episodes are stories that Kafuka makes up to poke fun at and to entertain her class, Itoshiki-sensei and herself. It explains why she's always around, and it even help explain the single-trait characterization and Flanderization of the girls and Itoshiki-sensei — it'd be damn hard to display your friends' full range of emotional depth in a verbal story, so Kafuka simplifies them. The connection with her name, particularly that it's explicitly called a "pen name", also makes sense.

Itoshiki is in Hell.
The world portrayed in Sayonara Zetsubou Sensei is very similar to Hell as shown in Johnny the Homicidal Maniac - just like Earth, but a bit weirder, and everybody is constantly driven to despair by minor annoyances. This means that Itoshiki died by suicide in the first episode for a crime which made him a target of Light Yagami. Light set Itoshiki's death to some time after the end of his natural lifespan, which is why he was able to survive a death note-induced heart attack - the reason he didn't die is that he was already dead.
 * Everyone else in his class was killed by Chiri on the train in the closing sequence because they were imperfect, and she then killed herself to make the numbers even.
 * ... Which would make sense, if you consider the ED to be a whole episode rather than a clip. If you look at the chorus part of the video, it looks like Kafuka is killed last, before Nozomu, then Chiri. Nozomu tries to catch Kafuka on the boat because by riding the boat, they would reach the world of the dead, and death is what Nozomu always wanted. Both possibility exists, if not more.
 * Everyone Is Jesus in Purgatory has left me in despair!
 * Come to think of it, if the opening is viewed as part of the same episode as the ending, the bondage scenes, Itoshiki running in terror, and the bit with Kafka at the end suddenly take on a very disturbing light.
 * It's Shinbo. You expect him to make sense?

World only exists in the mind of one character
In this tropers opinion, the world in SZS only exist in the mind of one of the characters, mainly Itoshiki's. He has been driven mad by so much despairing he thinks he is a teacher in a class of misfits when really he is in a psychiatric ward and he is locked in a strange delusion in his own mind. Alternatively, it could be all in the mind of Kafuka and she is the one in the ward...
 * Alternatively, Itoshiki is still in a mental ward, but rather than the other characters being figments of his imagination, they are other people in the ward (thus explaining why almost everyone in the class is crazy in one way or another). Being an adult among children, he deludes himself into thinking the meeting area intended to allow communication is a class he is the teacher of. He thinks that area is a school and the hallways streets, rooms houses. When he tells the class not to talk to him outside of the classroom it's because some people in charge of the ward were warning them not to. The episode when he went back to his family was the one day when he and the others were allowed to see how much better they were able to live in the real world. The 'normal' girl (whose name I can't remember) is part of the staff, assigned to that room to keep everyone in check.
 * I get it.

Kafuka is schizophrenic
This troper believes that "Kafuka Fuura" is juts a personality created by the girl to be able to cope with her tragic past. It is actually mentioned in the series that Kafuka is not her real name. In response to Kimura having developed split personalities from trying to adapt to Japanese and whatever-the-country-she-lived-in culture, she mentions having done a similar thing in order to fit in after moving to another part of the country, but she mentions creating two personalities in addition to her own. Maybe one of those is her true self, and she created the eternally cheerful Kafuka so she wouldn't have to deal with her father and mother trying to kill themselves and all the other nasty stuff that happened to her. Her traumatised real persona occasionally surfaces, explaining her yandere-moments and the fact she's seemingly unaware that she's thinking about killing he other students in one episode(as that was her true persona thinking).
 * This seems supported by the fact that in the second season Kafuka disquises herself as a college student who seems attracted to Nozomu. Another persona created to deal with her attraction to her teacher? In any case, the way she brandished that knife couldn't have meant good...
 * Kafuka was making shit up to jump on the bandwagon and she disguises herself as the college student in order to jump inside Nozomu's hakama. Though I would like to see if they would actually use the yandere thing. Plus her speculated name is An Akagi (reference to "Akage no An" a.k.a. "Anne of Green Gables"). (see Ep 1)
 * In the OVA, we actually see a preschool Kafuka wearing a nametag that reads 'An'.
 * Schizophrenia is not dissociative identity disorder. Having multiple identities is in no way a symptom of schizophrenia. Not even close. It isn't even a related disorder. Different thing entirely. Look it up.
 * Meru, on the other hand, could be borderline or undifferentiated schizophrenic. Coprolalia, no nudity taboo, bizarre delusions that she's in an anime, negative affect... they all fit.

Kafuka and Itoshiki are of the Nobilis
Being known in better circles as the Lady of Hope and the Duke of Despair. This explains the gratuitously grand or 'mythic' portents that surround seemingly random actions: when any part of your life could be a part of a symbolic Flower Rite against the fabric of reality, even taking a bath can become epic. Note the hot springs episode in particular, which shows the horrors an Excruican attack on the characters' natures themselves.
 * This is the most brilliant theory I have ever seen. Additionally, perhaps Fuura's inability to see things in a negative light is a Gift of Domain, as is Itoshiki's ability to do the epic "I'M IN DESPAIR!" thing.

The high school is actually a juvenile insane asylum.
Almost every student in the school suffers from some kind of certifiable psychosis. They were all deemed too dangerous to have around regular students and teachers, so they've been sent to an institution for mentally ill teenagers. The only exception is Nami, who commited herself to the asylum to prove that she isn't normal.
 * This is what this troper thought as well. But this may be because he finished reading Cross†Channel the day before watching SZS
 * Alternate possibility: Administration just gave Nozomu all of the crazy students for some reason. Maybe they hope that the psychoses will all cancel each other out, or maybe they think Kafuka will snap and take out all the problem students.

Kafuka is actually Nozomu's daughter
Think about it. She claims her father kept trying to "make himself taller". Nozomu keeps trying to do that as well. They may say he is only 23 but people lie about their age all the time (And for that matter how can someone become a teach at that age given his level of expertise. In the few times he is teaching he seems awfully knowledgeable...) It could be he has, from a previous suicide attempt, damaged his memory enough that he no longer recalls his original identity, age or family and has made up this new identity out of trauma and possibly to avoid the debt collectors? Also it would explain his aversion to Kafuka and Kafuka's constant attraction to him. She is also such a polar opposite to Nozomu there is no way it can be conincidental...or is this just me rambling on now?
 * Jinroku says Nozomu is an exceptional teacher for someone so young. So there.
 * Ah...but young in relation to who or what? Someone in their 50's? 40's? 30's? There are some professions where a fairly advanced age is still considered youthful in relation to the rest of the group/institution/company/agency/whatever...
 * It says a lot about this series that incest is being invoked to make things less confusing/menacing. Although, in the light of Kafuka's...repressed aggressions, it raises a disturbing question of its own: where is her mother?
 * While this troper finds it highly improbable that Itoshiki could be anyone's parent (he's distinctly young and even more distinctly not capable of a relationship), it's not difficult to guess that Kafuka's mother is probably in an asylum somewhere after that one time, and her father might be dead, for all we know.
 * The new OP to the 3rd season doesn't help matters, IMHO, as it shows Nozomu catching Kafuka as she fell. Indeed, all the openings show the two together in some way, so there may be some link there...
 * The end of the OP to the 1st season implies it's the other way around: A pregnant Kafuka and Nozumo in fetal position with an umbilical cord (rope)

How the series will end
The story will end in a simple way. Kafuka will finally snap and just kill everyone and then kill herself. The only survivor will be Itoshiki who will promptly try to kill himself, and fail again.
 * At this point, he will realise how lucky he is to be alive, and will, for once, feel joy.
 * Alternatively he could end up witnessing God's Last message to His creation and finally understand happiness, thus ending his term in purgatory.
 * Or he could despair at the fact that God's Last Message to His Creation is "We apologize for the inconvenience."
 * Conversely, Kafuka leaves herself and Pink Supervisor alive (I can't see Kafuka killing herself, she's just not that person, even if she were to snap) and they then travel to a new school. Kafuka probably holds all of her negative emotions inside (which can be seen in the Meru episode when all of that Black Speech coming from her eyes) and needs to let it loose every once in a while. Nozumo will inexplicably end up teaching another crazy class, looking on them with pity because he knows that soon they will be slaughtered by Kafuka.
 * This troper thinks Kagerou will survive as well, because no one really notices him in the killing spree. This doesn't help Itoshiki, though, as he doesn't notice him either.
 * When Kafuka herself is truly in despair, the series will end. Although logically Zetsubou-sensei should be dead as well, but the two events are hardly mutually-exclusive.

Mayo is related to(possibly the sister of) Ryuji from Toradora
Both have "evil" eyes. Both of them know people who don't see them as evil. Both of them are never seen together with their father. When you also add in the fact that SZS is referenced in Toradora...

Itoshiki doesn't actually want to die.
While circumstanial evidence that Despair-sensei has shown up from time to time it wasn't until Episode 1 of Goku Sayonara Zetsubou Sensei when he hung himself.
 * This is given away by his occasional Catch Phrase, "I could have died!" He uses it whenever someone's attempt to stop his suicide ends up endangering his life in some other way.
 * Further commented on in the third part of Episode 8 of Zan, where Kafuka comments "I've come to understand that you have a voracious appetite for life, teacher." I mean, if Kafuka noticed, then it's not really a secret.
 * Also, his nooses aren't tied properly. Nooses are supposed to tighten around the neck, but when he "hangs himself" from them, they stay loose. He's not suicidal, just an Attention Whore.

Ishitoki has Mytho's 'despair' heart shard
And once it's removed, the series will become very boring.
 * Also, Kafuka has Mytho's 'optimism' heart shard

Itoshiki is L in the afterlife.
Based on the scene where Itoshiki collapses and sees Light's face exactly as L did. Ryuk said there's no heaven or hell in the Death Note world, so this is probably some strange place with no clear evil/good alignment, just a person's self delusions and fantasies coming to life.
 * Itoshiki is a dead soul that will be consumed by despair and become Ulquiorra Schiffer.
 * That's not how Bleach works. The natural cycle is living world to Soul Society then back to the living world.
 * Yes it is. Hollows aren't part of the natural cycle, so a dead Arrancar would go to Soul Society. If Death Note takes place in a version of Soul Society, it fits: reincarnation isn't Hell or Heaven.

Itoshiki is a distant relative/alternate universe version of Bernard Black from Black Books.
Just look at them.

Itoshiki is Pandora's Box in human form.
Most versions of the myth say that Hope was trapped in the box. But if you think about it, if unleashing the evils from the box is what allows them to be experienced, wouldn't you want Hope to escape? This Troper once read a version saying that what was trapped in the box was, in fact, "Despair." Were Despair to escape, humanity would be deprived of hope. Thus we come to my Wild Mass Guess, which suggests that, through some form of magic or another, Itoshiki is, in fact, the human form of Pandora's Box, which holds back the bulk of the world's Despair.
 * It has also been said that HOPE was the WORST of all that was kept in Pandora's box.

Kafuka is an alien come to destroy humanity.
This might not count since the writers seem to be pushing this half the time, but really - the rather obvious "change of landing destination" from the "soft landing" episode, her blatantly fake name, her communciation with the planet Pororokka at the end of episode 4, her latent desire to kill... hey, if Ford Prefect could mistake a car name for a perfectly inconspicuous human name, who's to say Kafuka couldn't mistake a fictional horror movie for a perfectly believable and not in any way abnormal story about what could happen to anyone's family member?

Itoshiki is immortal.
That's why he doesn't die when he hangs himself. It also explains that scene where they're about to bury him and he just comes back to life.
 * This also explains why he's suicidal. Who Wants to Live Forever?

Kafka is observing either Itoshiki or the class as a whole.
We know Kafka is a pen name. She has a college student alternative persona. Either she skipped ahead or is older than she looks, but the college student is her real self. She is observing everyone for a book.

Kafuka and Nozomu are meant to balance each other out
Think about it. Nozomu seems like a depressive teacher who wants to die, but really is just an eccentric and harmless death fetishist. Kafuka on the other hand seems very optimistic and harmless, but may very well be a yandere that will kill everyone. The two balance each other and creates a dynamic that keeps each other in check and actually gets things done. Of course, this is not necessarily a good thingâ€¦

Nami's quirk is being obsessive about not having a quirk.
Or she's a Time Lord. Having two hearts isn't very normal.

In a future chapter:

 * Itoshiki will get contacts and then despair about putting something directly into his eyes.
 * Kafuka optimistically notes that in a few hours, the sun would rise.
 * Chiri digs a Burmese tiger trap with her shovel. Itoshiki falls in, as does Matoi and the entire stalker chain.
 * Kagero buys a toupee, and is noticed due to how fake it looks.
 * Kaere joins the Church of Scientology.
 * Nozomu already got contacts once.... and Kagero did, get a wig, but still no one noticed. And these both happened a while ago.

Kafuka's parents really did think that trying to make themselves taller would make everything better.
But their unsuccessful attempts at making themselves taller left them in despair, which made them suicidal.

Mr. Despair is a Waste-Lock/Flusher

 * Think about it. (But not too hard, or you'll notice the flaws) While Johnny is in Hell, Satan says that most "flushers" turn their negativity in on themselves rather than on the outside world (Ranting doesn't count as turning it on the outside world). Both Johnny and Itoshiki are in despair about society (Their methods are a wee bit different of course). Both attempt to end their own lives (kinda-sorta for Itoshiki, but just ignore that because I'm trying to make a point that doesn't even make any sense). Hell, they almost kinda look sorta similar (Both tall, thin, and black hair. Jhonen has said that Johnny is more "beige" than pale, but JTHM was in monochrome, so it counts). Mr. Despair seems incapable of permanently dying (and Johnny was brought back to life). Ultimately, it could be said that their cosmic positions are, if not the same, then at least very very similar (Hey look, a parenthetical comment after every sentence!).

Taro Maria Sekiutsu is only about 10-13 years old.

 * Notwithstanding the fact that she is an illegal immigrant from a disaster stricken land and thus likely to be smaller than average due to long term poverty, the fact that she bought her identity from a boy proved she wasn't too worried about making sure it would convince any authorities that she is who she claims to be, thus I seriously doubt that she cared too much if the new ID would be suitable for her agewise.
 * In other words you are saying that she's reaqlly a 12 year old girl who just happens to have bought an ID from a 16 year old boy? Makes perfect sense in the context of this show.
 * She's also not as stupid as you think she is. She's ignorant about many things because she's not Japanese and she often behaves like a kid because she's actually 10 years old.

Kafuka is another Suzumiya Haruhi-person.
Think about it. Her list of hopes despairs for the future has her wanting to become an alien, a Time Traveler, and.... God. And her image song "Kamisama to no Yakusoku" has her inviting aliens to earth so she can play with them.
 * Yes... but she has none of the agression, Pride or melancholy over normal society you'd associate with Haruhi. If you must bring up old memes technically Kafuka, Nozomu and Chiri would all be separate parts of Haruhi split apart for some reason.
 * Well, Kafuka is a Genki Girl and she wears hair decs like Haruhi.

Itoshiki is actually Straight Gay
Which is why he is completely impervious to the various girls' advances. And his deep despair actually has only one cause -- Gayngst.
 * Actually, he might have slept with a man once. But since it looks like the guy is just starting to coax Itoshiki's clothes off, we don't know if he went through with it. However, when you consider the situation as a whole, this might just be evidence against the above theory. He had some weird motives for sleeping with/almost sleeping with the guy. And there's the face he's making. Funny when a guy accepting the advances of another man seems to be the only indication of his possibly being heterosexual. Only this show...

Kafuka is...

 * Giygas. The Pororokka aliens abducted two humans from Japan, who studied their secrets and then escaped, taking Kafuka with them. However, the true depths of the alien powers were so terrifying that Kafuka's father went mad and tried to kill himself. As she grew up, secret agents of the invasion force frequently chased them and tried to take Kafuka back, but her mother lied and told her they were things like debt collectors; she has a fake name for her own protection, although she isn't aware of it. Her mother's exorcism was really her being tortured or driven mad by the aliens. In the future, Kafuka will discover her origins, go mad with evil power, and possibly destroy the world/reality as we know it.
 * A fairy. The reason she's so insanely cheerful is because she doesn't have human emotions, per se. That's why she doesn't understand the reality of the cast's problems, and why she says such bizarre, Nightmare Fuel-laden things.
 * A god, like Oyashiro-sama. When she was sacrificed in the past, she gained divine powers to alter reality. The rest of the cast is suffering from Hinamizawa syndrome, and will eventually go mad (er, madder) and kill themselves. Her existence is linked to Nozomu, so she keeps trying to prevent his suicide and resets the universe after every episode when something goes crazy/wrong. She's not perfect, though, and the Groundhog Day Loop their school is in as a result has also made her a little...unhinged.
 * Half of the reincarnated soul of Franz Kafka. Itoshiki is the other half.
 * Or just a Type A Stepford Smiler. Maybe she really does just act all happy for the sake of everyone else, and doesn't ask for attention or help DESPITE her abusive childhood.

Itoshiki is the author of the book of Ecclesiastes
Seriously, go read it, there is no other explanation; This Troper, for one, cannot read it without imagining it in his voice. ""Everything is meaningless," said the Teacher, "completely meaningless!""


 * Mindscrew xD

Maria is the Great-Great-Great-Great Grandmother of Ed from Cowboy Bebop.
Speaks for itself, really.
 * Those are some genes she's got...

Itoshiki is a grown up Shinji after he halucinated the events of Neon Genesis Evangelion

 * Who is the only other person that is this depressed in any fictional work aside from Marvin from Hitchikers Guide To The Galaxy or Eore

This entire show is because Despair of the Endless got bored.
Hey, if Dream and Death can make a guy immortal based on a whim...

NozomuxDespair.
He's in love with despair. He's with one of his students because, besides the fact that, you know, he's not allowed, but because...he's in a committed relationship with Despair!
 * Despair could be a person, and he's just making inside jokes about this.
 * Does Harumi ship them?
 * So when he says he's in despair, he really is in despair.
 * Are we talking about Despair of the Endless, here? If so, Squick.

Kafuka will grow up to be Asami from Audition
Because they are so much alike. You could consider Kafuka's "college student persona" as the first draft of the Asami identity. Presumably, Kafuka picked up some tricks from Chiri.

Kou from Arakawa Under The Bridge and Izaya from Durarara are members of the Itoshiki family.
That they have different names can be explained by the Itoshiki family's power- they were able to ensure that the characters were given pseudonyms. Kou could easily be the Itoshiki who is Majiru's father and was disinherited and abandoned him. Presumably, he had a falling out with his father and decided to live under the bridge permanently.

As for Izaya, his parents go for weird naming, which is in line with the Itoshiki's- I figure he's either an illegitimate relation or perhaps the child of Nozomu and Kafuka- he sounds like Nozomu and has Kafuka's love of mischief. Finally, while both characters look different than Nozomu, this is a product of the art style; they actually probably look a lot like him.

Kafuka actually has a normal family life.
Think about it. Maybe not "normal," but not as dark as we think. Her parents might be as optimistic as her and may be teaching her to be the same. Maybe she's just making the bad stuff up. Maybe she's exaggerating. This could be an instance of the "Abiru's abusive dad" rumour.

Kafuka is actually a Magnificent Bitch who has been secretely trying to kill everyone since the show began.
It's mostly suggested that she's a Stepford Smiler who will eventually snap and kill everyone, but if you look at her track record, she's done a pretty good job of trying to kill people anyway. Every time she tries to "help" it ends up getting worse; Season 1 alone has several moments were she either nearly kills someone or scares them shitless. In truth, she actually delights in seeing suffering and death, and hides behind a sunny disposition to keep anyone from noticing. This is also why she's taken such an interest in Nozomu. Every time she counters one of his class discussions, it tends to go badly for him and leaves him in despair. The first ending focuses a lot on her as well, and particularly her relationship with Nozomu, but these aren't images of her snapping; they're of her mind in the moment, and her various plots of maim and torture using the best weapon she has; love and happiness. She's a psychopath who literally knows how to "kill 'em with kindness".
 * Isn't that canon?

Matoi is actually an Empty Shell.
Her defining personality trait is supposedly Stalker With a Crush, but seriously, since when is that a unique trait in this series? She's actually a "personality leech" who drains away the outlook of her latest victim to compensate for not having a worldview of her own.

Kafuka is a Reality Warper.
Her overly optimistic and/or bizarre takes on reality have been shown to come true. For instance, Kiri (somehow) ultimately did turn out to be a zashki-warashi. Also, Kafuka's refusal to believe Nozomu was trying to kill himself has been borne out. It's ultimately revealed that he deliberately sabotages his suicide attempts so that he won't die (i.e. training his neck muscles), and is really more of an Attention Whore. Moreover, since Kafuka met him that day, it seems that nothing can kill him.

The high school is some kind of Extranormal Institute or School for Scheming.
This is sort of inspired by the episode where the class breaks Nozomu out of confinement, as well as an instance in the manga where Chiri tries to act out the plot of Battle Royale. While Nozomu and the class are unaware of this, they were actually selected as part of a Government Conspiracy to train agents that will help free Japan from its "peacetime boke" (see that episode with Maria) and allow it to Take Over the World. The project is funded by Nozomu's father, who is both one of the wealthiest people in Japan and a member of Parliament. The cast's skills are as follows:
 * Harumi is an amazingly gifted athlete and would have both combat skills and would easily infiltrate a building.
 * Chiri is clearly a very skilled killer and has clairvoyant abilities.
 * Abiru apparently has the best grades in the class and can strangle people with her bandages.
 * Usui can turn himself invisible.
 * Kafuka is a Master of Disguise and likely could be a competent assassin. In one episode she has access to secret information.
 * Kaere has been shown to be fairly athletic and is being molded into a Honey Trap.
 * Matoi can follow someone everywhere.
 * Kiri is skilled at fitting into confined spaces and could be Mission Control.
 * Nami, being utterly normal would be the perfect spy, functioning as The Nondescript.
 * Jinroku is a former Yakuza assassin.
 * Chie would probably be a good Honey Trap.
 * Nozumu is just immortal.
 * Plausible evidence.

Nozomu Itoshiki is The Very Hungry Caterpillar
He already ate his way through a red apple. Now, he's in this pear.
 * What a very cute pun ^__^

Kafuka is a Kira
(tl;dr warning)

Sometime before the show started,Kafuka received a Death Note in a manner similar to Light and also decided to rid the world of 'undesirables'. She killed her parents first(Have we actually seen her parents,other than in flashbacks?) and came up with the college student persona so she'd have a someone to place the blame on if she ever got caught. A couple months in,she met Itoshiki, whom she fell in love with. She writes in her Death Note that he'll kill himself after she dies to make sure that he wouldn't leave her(which explains why he doesn't die in situations that would kill a normal man,why she's never worried about him committing suicide and why he's chasing after her in the first ED). She enrolls in his class to be close to him,only to find that the entire class is filled with 'undesirables'(with five exceptions,but I'll get to that). Realizing that she can't kill them all or risk being caught,she comes up with outlandish excuses for their psychosis,so that she doesn't feel like she's failing herself(hence her declaration of 'How could a ____ like that exist so close to me?!' a.k.a. There's no way I'd allow something like that to go unpunished!). She never gives out her real name and tries her best to creep the other students out,hoping that they'll move away so their deaths will be harder to trace back to her. Every mention of 'pororoca' is a reference to Shinigami so that her five subordinates will know what she's talking about and when she wrote 'God' on her career hopes survey she was admitting that she's trying to become 'God of the New World'. Her five subordinates are the only other people she feels she can trust in her school:

Chiri Kitsu:The Second Kira. They have similar goals,Chiri will do anything to see that the world is in perfect order and she was born with a shinigami eye.(It's also why the two of them hang out so much,even though they seem to have nothing in common and why Kafuka never makes excuses for Chiri's behavior.)

Jun Kudo:His love of stories led him to help Kafuka and Chiri complete their goal(He wants to be able to tell their story once they create the new world). He reads the news paper to find out about other 'undesirables' that Kafuka may have missed and as far as we know he doesn't have any psychosis.

Chie Arai:The Third Kira. She has shinigami eyes(hence everyone's fear of her stare) and seems to have a superiority complex(she and Kafuka also hang out a lot).

Nami Hito:In one of Nami's flash backs,there's a girl named An who calls her normal or ordinary,if the theory that Kafuka's real name is 'An Akagi; is correct then that girl is most likely Kafuka(The girl even looks like her). Perhaps Kafuka started the whole 'normal' teasing(the way she goes on about it,it seems like something that's followed her around) and has roped her into helping by promising that there will be no 'ordinary or normal' people in the new world. Because she's so normal,people probably don't look twice when she starts snooping around and digging up dirt about them...

Maria:Even though she's an illegal immigrant,Kafuka can't bring herself to kill her and much like Nami,she's being used for recon.(She seems to have the same creepy thing going on that Kafuka does)

Abiru Kobushi and Kagero Usui are the only ones who notice something is up,the former will soon die in an animal 'accident' and no one even sees the latter(and he'll probably kill himself after Abiru dies anyway),leaving Kafuka undefeated.
 * Some related ideas: Kiri and Kafuka were both born with the shinigami eyes (hence why they both have red eyes). Kiri became a hikikomori because she didn't want to always see how long people had to live. On the other hand, Kafuka went mad from the revelation. Both of them are drawn to Nozomu, because similarly to Rincewind, he has a weird combination of amazing luck and awful luck with the result that it's not clear when/if he'll die. Also, Chiri is definitely Kira material. She and Mikami would be a perfect couple.

Sayonara Zetsubou Sensei is the personification of TV Tropes Expy in the form of an anime.

 * While it is true that SZS focuses only on social and cultural tropes that apply to Japan, you notice that in every episode, Itoshiki-sensei introduces a trope in a form of a rant and then his students chip in and bring up examples including subversions, inversions, deconstructions and other ways of playing with a trope, all in an entertaining form, just like TV Tropes.

Nozomu Sensei isn't trying to hang himself to die, he's just experimenting with auto-erotic asphyxiation.

 * Let's look at the facts:
 * 1) He trains his neck muscles at the gym so that his neck doesn't break when he hangs himself.
 * 2) He frequently says "I could've died!" if he actually is in danger of dying. And...
 * 3) He has a whole classroom full of attractive high school girls (including his sister!) who want him.
 * He probably tries auto-erotic asphyxiation as a way to...relieve himself of his dispair and the sexual tension in the classroom. But of course, with students like Kafuka and Chie, he never gets around to actually trying it.

Nozomu is a ghost who is the embodiement of all of the despair in the world.

 * Panty and Stocking will eventually have to take him out.

Some of the characters are inspired by Peanuts
The series has made some direct references to Peanuts, and this makes a surprisingly large amount of sense:
 * Charlie Brown's equivalent would of course be Nozomu- same melancholy Butt Monkey characterization
 * However, his nephew Majiru (see below) is voiced by Akiko Yajima, who also plays Chuck in the Japanese dub of the Peanuts specials.
 * Lucy is Chiri- the bossy know-it-all
 * Linus is divided into Majiru and Kiri- Majiru has the personality down and Kiri is always wrapped in a Security Blanket
 * Marcie would probably be Harumi
 * Pig Pen is naturally Chiri's messy sister, Tane
 * Snoopy is that weird Emperor Penguin thing.
 * Kafuka is kinda similar to Sally...at least on the surface. Of course, as with many of the Peanuts cast, one wonders with her (Sally) as well.

Itoshiki is Erebus sealed into a human form.
The reason that he's constantly in despair and trying to die is because he's host to humanity's collective death urge. However, his own human will wants to live, so he constantly resists Erebus' desire to reach for death.

If Studio Shaft does decide to animate the last few volumes now that the manga is coming to an end...
There will be at least one Madoka Magica reference/plug per episode, just like Haruhi in Lucky Star (especially with Kafuka and Kyoko sharing a VA).
 * For instance, Harumi might take Chiri to Comiket, and Chiri will notice a stack of Madoka Yuri Doujinshi, then complain that there's not a precisely equal amount of yuri and Yaoi doujins.

Kanako Oura is The Stoner.
Maybe she should convince Chiri to try some of her stash.

Nozomu wrote Madoka Magica, at least in the Zetsu-verse.
Leave it to him to come up with such a nihilistic, depressing series. However, the fact that the title character shows that even he still has some spark of idealism left in him...hence why he's always unsuccessful at suicide, and why he hasn't been attempting it much lately.

"I'm in despair! The revelation that trees suffer from epilepsy has left me in despair!"