Mood Swinger

""Last night was an A-1, tip top clubbing jam fair. It was a sandwich of fun on ecstasy bread, wrapped up in a big ball like disco fudge. It doesn't get much better than that, I just wish that sometimes I could control these FUCKING MOOD SWINGS! So what did youse two do last night?""

- Tyres, Spaced

A character whose personality isn't marked by any set mood, but by their tendency to swing between moods drastically. Sometimes (if the characters around them are lucky) there's some sort of warning of an impending mood swing -- or at least a recognizable cause -- but there may just as easily be no warning whatsoever.

Frequently this is combined with emotional lability, so they skip any emotion that isn't extreme. They're never just happy, they're the cheeriest Genki Girl in the world. They're never just sad; they're on the verge of suicide. They're never just angry; they're filled with Unstoppable Rage. And they can flip between any of them at a moment's notice.

Though they may be referred to as "bipolar", their mood swings are generally much more abrupt and frequent than the periods of mania or depression associated with type I of real-life bipolar disorder. This can, however, be a facet of type II bipolar disorder or borderline personality disorder.

This is a stereotypical trait of women who are currently menstruating or suffering from PMS. It is Truth in Television, and fairly common at that, but not typically as extreme as fiction portrays it to be nor as universal. Also, not every woman whose mood is affected by menstrual hormones will be susceptible to every mood; some get stuck swinging into one mood and temporarily become a Fragile Flower or acquire a Hair Trigger Temper. Since the same hormones are involved, pregnant women are also known for being Mood Swingers.

The Mood Swinger as a Love Interest frequently fills the role of the Tsundere. This is also a common trait of The Caligula.

For even more extreme cases, see Hair Trigger Temper, Split Personality, Jekyll and Hyde, and Yandere.

Anime and Manga

 * Kagura from Fruits Basket. She seems cute at first, but whenever Kyo's around she becomes a combination of a Yandere and a Tsundere.
 * In the beginning at least, Kyo came across as this since he had No Social Skills and had a tendency to snap at people he wasn't mad at. So he'd yell at someone, apologize, then yell at them for not understanding him. Then apologize...
 * A good deal of the characters from Sayonara Zetsubou Sensei. Namely Kafuka who's somewhat similar to Rena, except she's even more overly optimistic.
 * Rena from Higurashi no Naku Koro Ni. This and the fact that she's a Nightmare Fetishist seems innocent enough at first, but then you find out she's a Grotesque Cute Yandere antagonist best known as the "Cleaver Girl" for her Ax Crazy tendencies. . The games hint she has a bipolar disorder, but it's exaggerated so it seems freakier.
 * Actually
 * Haruhi Suzumiya comes close. Now she's a cheerful Genki Girl, the next scene she's abrasive, confrontational, dominant and almost narcissistic, after that she may become extremely melancholic. There are reasons for her mood-changes, but sometimes it just appears randomly.
 * You know, just like a real teenager.
 * Naomi in Zettai Karen Children started off being the calm, sweet girl all the time. Once she realized that her supervisor Tanizaki's treatment of her was why she was having trouble with her powers, she lets loose and from then on shows no restraint in throwing him into a wall when he gets too close. Her Code Name even changes from "Kitty Cat" to "Wild Cat" in the process.
 * Ayukawa Madoka from Kimagure Orange Road is pretty bad about this, though her swings are more day to day than moment to moment. And of course she's the Tsundere leg of the Love Triangle.
 * Karin from Naruto. Karin has a fluctuating personality, at times appearing stern and tough and Tsundere and other times appearing carefree and highly flirtatious, but only around Sasuke.
 * She even uses it as a way to escape some guards in Konoha.
 * Jugo has it even worse from a Gentle Giant to Ax Crazy. He even been named Jugo "of The Scales".
 * King Hamdo from Now and Then Here And There takes this trope to Nightmare Fuel extents. His moods usually switch from petty, to cruel, to violently moody, to pathetic, and back, usually over the course of a few minutes. Regardless of his mood, he is without a doubt, a Complete Monster.
 * Misao Mikogami from Kami Kaze can be a fairly cheerful and fun-loving teenage girl, nice to anyone who needs a hand, and will stand up for someone when they need it. Of course, say the wrong thing around her and her mood will change so fast that you won't even have the time to mouth the words Oh Crap before you're standing under an ocean of water with your current surroundings gone so far beyond the Godzilla Threshold that you'll be glad you're not around to see the aftermath. And that's not counting the times you've pissed her off enough that she decides to play around with you for a little while. Did this troper mention that she's the nicest deity in this series?.
 * Alois Trancy of Black Butler. Throughout the first episode he switches from cute and innocent to Ax Crazy so many times it could make someone dizzy.
 * Harry of Outlaw Star.
 * Kamille in Zeta Gundam can go from personable and friendly to teenage angst-fest in the blink of an eye (Not Hyperbole). It's oftentimes difficult to tell what exactly set him off.
 * Revy of Black Lagoon normally displays a wide range of emotions, all the way from affection to psychotic rage to calm boredom.

Film - Animated

 * Boingo from Hoodwinked acts like this once he drops his Tastes Like Diabetes facade and starts acting like a supervillain. The commentary remarks that on one occasion they couldn't decide which take to use (maniacal, verge of tears, etc), so they just decided to string them all together to very good effect.
 * After escaping from the tower in which she's lived her whole life without leaving in Tangled, Rapunzel swerves wildly between unrestrained joy at being liberated ("BEST! DAY! EVER!") and crushing guilt at breaking the promise she made to Mother Gothel to never leave the tower ("I am a despicable human being.").
 * Basil from The Great Mouse Detective certainly swings from manically happy to crushingly depressed and back to manically happy again quickly. Of course, this is because he's based on Sherlock Holmes, who was possibly bipolar, and definitely a massive cocaine addict. So either Basil could use a little lithium, or he's gotten into a bad, mouse-sized vial of seven per cent solution (an expected hazard of living under Holmes' floor).
 * The Nightmare Before Christmas: Jack Skellington, particularly during his BSOD Song, "Poor Jack".

Literature
""Now, Tinkerbell was not all bad. At least, she was not all bad all the time.""
 * Tonker in Monstrous Regiment has only two moods: calm and berserk. The description used in the book is "has no middle gears."
 * Peter Pan: This is Tinkerbell's original characterization. J.M. Barrie explains that fairies are 'so small they only have room for one feeling at a time.'


 * Hell, Peter's like this at least as much. Having been raised by fairies may have something to do with it.
 * Less than halfway through the first novel, it's easy to see where theories of Sherlock Holmes being bipolar come from.
 * Vlad Tepes in Count and Countess, usually to scary degrees.

Music

 * Relient K: Whoever the song "Mood Rings" was about: "First she's Jekyll and then she's Hyde... at least she makes a lovely pair", indeed.

Live Action TV
""""
 * Dick from 3rd Rock From the Sun: "I find you pompous, judgemental, and completely self-absorbed. Would you be my friend?"
 * I think that indicates more that he finds those traits to be friend-worthy, as he is all those things himself.
 * Agreed, though Dick does fit this trope. Maybe a better example would be something Mary Albright said early on: "You act as if you're feeling everything for the first time, you have no control over your emotions!"
 * Tyres from Spaced does this frequently, with the camera angle often changing with his mood. Explained as a long-term side-effect of taking waaaaaaaaay too much ecstasy.
 * Kevin the Teenager from Harry Enfield And Chums is a nightmarish example.
 * Cat in Victorious can go from happy to sad in under 4 sentences.
 * Sherlock's Jim Moriarty has, to say the least, a habit of doing this.

Theatre
"Lucy: ...And don't forget to change your facebook status to in a relationship. That way our profiles will be linked together like little love handcuffs.
 * Lucy from 13 has this dialogue with her boyfriend:

Brett: (To Cassie, who is walking by) Oh hi Cassie.

Lucy: Are you FLIRTING with her?!

Brett: No, I was just saying Hi.

Lucy: So you're saying I'm fat?

Brett: No.

Lucy: Well, you never say anything about how amazing I look anymore.

Brett: Lucy, you are driving me crazy.

Lucy: See? Now that was sweet. And sweet makes me sweet. Got it?

Brett: No."

Tabletop Games

 * Malfeas in Exalted is known to be bipolar on a huge scale, but the real Mood Swinger among the Yozis is Kimbery, whose affections change like the tides - as soon as she's disappointed by you at all, she goes loveloveloveloveloveSOMUCHHATE. Being in the second category is a death sentence; the first, a death sentence suspended until you inevitably enter category two.
 * One of possible monsters in Munchkin Card Game is a "bipolar bear" - he will attack you furiously or run away, depending on its current mood.

Video Games

 * The Happy Mask Salesman in The Legend of Zelda: Majoras Mask. There are literally no physical transitions between his extreme emotions.
 * Arcueid from Tsukihime. Nothing too drastic though, unless you make her really angry.
 * Tira is either bloodthirsty-cheerful or bloodthirsty-angry. She can change semi-randomly during a fight.
 * In her second appearance this escalated from Bipolar, to actual split personalities and her fighting style changes depending the current mood/personality
 * Persona 3 While not as extreme as some of the others on the list, Yukari Takeba frequently goes through random moodswings through the course of the game.
 * Perfectly understandable too, given the fact that, before the events of the game, she was (for the most part) a normal teenager.
 * The Dance Dance Revolution announcer, or at least the one from DDR Hottest Party. He lavishes praise on you when you're doing well or even just okay, but the second your dance meter falls into the red he'll angrily demand that you stop sucking. Also, when you idle on the song menu he demonstrates all the patience of a spoiled six-year-old ("BO-RING!").
 * In Psychonauts, you delve into the brain of a former actress to control her mood swings. Her mind is represented by a stage where can change the atmosphere from cheery to depressing with a switch.
 * Arguably all characters in the Galactic Adventures expansion for Spore, as players are only given 5 emotions to work with (happy, sad, angry, scared, and neutral which is just a different version of happy) when making dialogue portions for their user-created missions, and they're all expressed in the most exaggerated way possible without and transitions between them. This also makes certain character types such as the Deadpan Snarker and The Stoic very difficult to portray believably.
 * Due to programming, Cole Phelps from LA Noire. During interrogations, he'll typically ask a calm, polite question, and then if you select "Doubt" or "Lie", abruptly start screaming obscenities at the suspect, then return to normal for the next question.
 * Wigglytuff in Pokémon Mystery Dungeon Explorers has this reputation (along with Hair Trigger Temper), though at first it seems like its an Informed Attribute. After you fail to bring back a Perfect Apple however, he literally almost blows up the guild. Besides that, the aftermath of his Curb Stomp Battle with Team Skull supports this.
 * Anders of Dragon Age II is stated in the Codex to suffer from manic and depressive phases as of Act III, due to the Sanity Slippage caused by his Demonic Possession. His dialogue throughout the game tends to reflect this, ranging from calm and caring, to snarky, to obsessively focused on his goals, to self-righteously grandiose, to self-loathing and miserable, to downright psycho, with alarming speed.

Web Comics

 * The fairy Red from Gunnerkrigg Court veers between smarmy affection, despondency, and rage. If anything, she gets worse after she becomes a human. (Maybe it's the hormones.)
 * Zimmy is similar, though her personality is a bit more subdued. (Read: not psychotic.) Her mood swings revolve around her friend Gamma. An in-depth analysis of Zimmy's issues on the matter would make this page about twice as long, but the short version is this: Gamma acts as a grounding wire for the bulk of Zimmy's Reality Warper powers, which she can't control, and thus keeps Zimmy's mind mostly at peace. Zimmy is nonetheless aware that she's not a lot of fun to be around, and is terrified that if Gamma thought she had any other friends, she'd spend her time with them instead of Zimmy; between this fear, and the power Gamma can't drain away, her overall reaction to the world is erratic and designed to keep people at arms' length by whatever means necessary.
 * Sollux of Homestuck has this problem, and tends to lapse in and out of Heroic Self Deprecation repeatedly. It's part of his overall theme of duality and bifurcation.
 * In DMFA, for the 'cubi it's a racial trait linked to their emotion based powers. A 'cubi is both mercurial and feels emotions more strongly than any other creature or being.
 * Jean Poule in The Inexplicable Adventures of Bob

Web Original
"Critic: A BAT CREDIT CARD???????!!! I'LL KILL ALL OF YOU!"
 * The Nostalgia Critic. All it takes is one bad move from a film and he'll go apeshit. Case in point?

"Terry: I just want you all to know that I don't care if you're a boy penguin or a girl penguin, I just... Aw, heck, I'm just gonna come right out and say it: I love you all to pieces!
 * The 20 Questions-playing Akinator can switch between smug satisfaction and red-hot rage between one question and the next, if what he thought was a perfect guess is thrown off by an answer that doesn't fit the bill.
 * Terry, the Bi Bi-polar Polar Bear.

Penguin: Oh, thanks Terry. We all love yo--

Terry: GO TO HELL!! *Runs off crying*"

Western Animation
"(sees dead bunny) "You... sick... bastard." (squishes dead bunny, merrily sends the bunny's kidnapper off in a rocket ship, and holds dead bunny up) "Heeey, little guy! Underneath all that precious fur..." (cuddles dead bunny mournfully) "All scared and all alone..." (pets dead bunny contentedly, starts singing) "If only~ they knew~ what it was like~ to be~ yyyyoooOOOOUUUU!" (rips dead bunny's skin off and gleefully wears it as a hat) "Jared, I want one of these for each and every inmate, not a moment to spare!""
 * Avatar: The Last Airbender: Theories/jokes about Katara being bipolar really took off after a scene in the ninth episode (after some hints in the first episode) where she explodes at Aang, becomes apologetic in the space of a few seconds ("Oh, my gosh, Aang, I'm so sorry! I don't know what came over me!"), only to turn around a few seconds later and angrily insist "No more apologies!" After her behavior in "The Awakening," a pervasive meme became "must be her time of the month."
 * Also Prince Zuko. One minute, he's calm, focused, and disciplined. The next, exploding in a flurry of grunts, growls, and fireballs. Even as a good guy, his mood doesn't improve much until the end.
 * Made fun of in one episode of The Simpsons. Homer takes sleeping pills to sleep well through the night and Lisa reads off the side-effects, one which is Mood Swings. Cue Homer repeatedly saying "Mood Swings" in various moods.
 * Hexadecimal in Re Boot has her mood swings lampshaded - her face consists entirely of a theater mask, and she has to manually wave her hand across it to change its exaggerated expression.
 * Lunch Lady from Danny Phantom who switches from kind, grandmotherly figure to full-blown "I'll KEEL you" mode at the drop of a hat. Her picked up the habit as well.
 * Superjail - The Warden.


 * Doctor Drakken from Kim Possible seems to go from mood to mood like an acrobat does on swings.
 * In the episode "Emotion Sickness", Kim and Shego become Mood Swingers thanks to the Moodulators attached to them. Ron and Drakken end up being on the receiving end of all of their emotions.
 * Aaahh Real Monsters had Ickis, the Ugly Cute lead with serious issues. He could go from nervous stammering to bouncing off the walls to grossly inflated overconfidence and back in minutes. And that doesn't even get into his bouts of wide-eyed idealism and naivete...
 * Heloise from Jimmy Two-Shoes tends to switch from Ax Crazy Enfant Terrible mode, to sweet and innocent mode, to Deadpan Snarker mode, to flirtatiously lovable mode (around Jimmy), to pissed off mode and back again.
 * Ren from The Ren and Stimpy Show.
 * Blitzwing the Triple-Changer from Transformers Animated, who switches rapidly between three personalities/moods: Icy (stoick and calculating), Hothead (enraged and Hot Blooded), and Random (who is... well, Random).
 * The titular Invader Zim.

Real Life

 * Rapid cycling bipolar disorder (in which the characteristic mood swings take place in periods of days or even hours, rather than weeks as is more typical) somewhat resembles this trope, and as noted above most fictional characters with bipolar disorder are depicted this way despite it being comparatively rare.
 * One of the key symptoms of Borderline Personality Disorder are rapid mood swings that happen within hours, at most a few days. It is clearly stated in the DSM IV manual: "6. Affective instability due to a marked reactivity of mood (e.g., intense episodic dysphoria, irritability or anxiety usually lasting a few hours and only rarely more than a few days)". This trope is so much a core indicator of that disorder, in fact, that it is debated to change its name to "Emotional regulation disorder" or "Emotional dysregulation disorder" because the term "Borderline" is outdated and carries too much social stigma.
 * Some people with PTSD have mood swings as part of the hyperarousal aspect of the disorder.
 * Ivan the Terrible had mood swings as a side effect of the quicksilver he used to treat his pain, one bipolar episode had him beat his son to death in a fit of rage. He reacted with devestating sadness.