Any episode of an animation that ends on either a major Cliff Hanger or a Downer Ending followed by... an upbeat end credits tune!
Moral Orel, once a lighthearted farce of small-town America, eventually fully transformed into a dark character study of its characters' depressing lives. Which is made even worse with the occasional heartwarming episode. No one is sure if it'll end with them all killing themselves or finding some kind of redemption.... They do. Or rather, Orel does, rising above the pain of his childhood to finding a legitimate version of the facade his parents "enjoyed." His parents, on the other hand...
On the flip side, if the intro song was in Japanese, that meant the episode would be wacky (featuring Mad Mod, Larry, etc.)
The "best" example of this would be "Birthmark", one of the darkest episodes in the series. It involves the end of the world, Raven's evil father Trigon preparing to conquer earth, Sladecoming back from the dead with new powers courtesy of the aforementioned Trigon, and Raven being informed that she will bring about the apocalypse. Then the next episode is about Beast Boy working at a fast food joint and battling evil tofu.
Also very high up, "Crash" and "Haunted" aired back-to-back and used Mushroom Samba to very different effect:
"Crash" involved Beast Boy accidentally infecting Cyborg with a computer virus that caused him to have Big Eater hallucinations while a shrunken-down Gizmo and Amoeba!Beast Boy tried to travel from his butt to his brain to stop them.
"Haunted", on the other hand, featured Robin inhaling a lungful of psychotropic dust from an old mask of Slade's, causing him to think Slade was back from the dead and trying to cause an earthquake. Worse, Robin's attempts to fight the Slade delusions hand to hand resulted in him nearly beating himself to death before he realized the truth note The delusions only manifested in the dark. And on top of it all, Cyborg discovers that the dust was activated remotely, hinting that Slade might not be dead after all.
The dark Season Finales of 1, 2, 3 (though season 3 wasn't really that dark), and 4 featured a very humorous (usually involving an alternate dimension) episode right before them.
In Season One, sandwiched between the first Red X ( actually Robin) episode and the Apprentice Season Finale was Mad Mod trapping the Titans inside his school.
Worth noting this wasn't entirely intentional, the episode Car Trouble, a relatively straight forward action story was suppose air before the Apprentice season finale, but Cartoon Network switched the order so it went Mask, Mad Mod, Apprentice two parters, Car Trouble; instead of Mask, Mad Mod, Car Trouble, Apprentice part 1 and 2. No doubt this inspire the writers to do the wacky before finale intentionally in the later seasons.
In Season Two, sandwiched in between the episode where Terra betrays the Titans by allowing Slade's minions to attack the tower and when Terra attacks the Titans under Slade's orders features Larry, a reality-warping dwarf version of Robin.
In Season Three, before the episode where Cyborg moves out of the Titans Tower to form Titans East with Aqualad, Bumblebee, Speedy, and Mas y Menos to fight Brother Blood, we have Mumbo trapping the Titans in an alternate dimension inside his own hat.
In Season Four, before the three part season finale featuring the end of the world through Raven, we have Mother Mae Eye, a witch who basically makes everything the Titans see an acid trip via cursed pie.
And one of the shorts in that Day In The Life episode has Iroh cheerfully dancing and singing through the city on a shopping errand, with the short ending on him, still singing that happy song, breaking down sobbing over a small memorial shrine for his dead son; ending with a dedication to Iroh's deceased voice actor.
The whole Ba Sing Se arc has a lot of Mood Whiplash. Take the episode "Lake Laogai" — Jet has just been left for dead in the shadowy headquarters of the Dai Li in what many fans consider one of the darkest and saddest moments of the season, if not the whole series. What follows immediately after? The triumphant return of Appa, complete with uplifting music and a dramatic rescue; and a joyous, tearful reunion between Aang and his beloved companion. And Jet is never even mentioned again until the third season. "The Earth King" seemed to be ending on a victorious note for everyone—which was, over the course of perhaps two minutes, mercilessly torn apart.
The last episode before the Grand Finale is "The Ember Island Players"; a Breather Episode where the Gaang watch a (very poor) play based on their adventures. Most of it is hilariousFlanderization of the main cast, but during the intermission, it whiplashes when the Gaang considers the mistakes they've made and their regrets. Then it goes back up and before having another Mood Whiplash at the end when the play ends with all of their characters dying and Fire Lord Ozai conquering the world, the crowd cheering, and the Gaang severely disturbed. After all, the play wasFire Nation propaganda.
From season 1, we have the episode "The Great Divide," which is widely disliked for being typical kid TV fare. Light-hearted, non-serious tone... Then we get to the next episode, "The Storm," which treats viewers to a rather scary flashback of FireLord Ozai scarring a 13-year old Zuko's face with firebending.
Mood Whiplash from the other end as well, as "The Great Divide" was preceded by "Jet", which involves the title character tricking the team to help him destroy a garrison of Fire Nation soldiers with a flood. Only problem? The garrison is in an Earth Kingdom village. Full of civilians. Which Jet chalks up to as "necessary sacrifices".
"The Chase." Starts with no one getting any sleep and yelling at each other and ends with Azula shocking Iroh with lightning, and Zuko refusing to let the group help him because he's so distraught.
During the Grand Finale, there's a scene where Sokka uses an absolutely hilarious announcement over the intercom ("Everyone please proceed to the bomb bay for hot cakes and sweet cream. We have a very special birthday to celebrate!") to get the crew of the airship he and his friends are taking over out of the way. You know, the airship that's part of the fleet Fire Lord Ozai is using to commit fiery genocide on the entire Earth Kingdom. Oh. The best part? It actually is some guy's birthday...and he got dropped into the ocean along with the rest of the crew and was probably left to drown.
Its Sequel The Legend of Korra also loves this trope, combining with a Wham Episode to show the whiplash for the extra kick. An episode can start off light and humorous but unexpectedly goes a dark turn and back.
In Book 2, "Beginnings", the life of Wan, the first avatar is shown. At the end, he gains the avatar state, triumphing against the spirit of chaos and sealing it away. There is a triumphant artshift image of him bending all four elements around himself, stopping warring human nations from attacking each other, while he declares and promises that he WILL stop the conflict created by the evil beings influence and bring peace to the world. Then it suddenly switches to the scene of a horrific battle that recently ended. With a very old, exhausted Wan in battle armor on the ground despairing that he couldn't keep his promise to bring peace and there "just wasnt enough time" as his old body finally gives out from a life time of constantly trying to end war, thus starting the cycle of reincarnation to maintain balance and end conflict.
Ben 10: Alien Force has a couple of episodes of this. The sixth episode, "Max Out", is very serious, with the kids discovering that the DNAliens are actually people infected by an alien xenocite and ends with Grandpa Max blowing up himself and the Highbreed Overlord. The seventh, "Pier Pressure", is very upbeat - it's about Ben's date with Julie, and is only minorly inconvenienced by the alien Ship's antics; there's no real villain. The eighth episode, "What Are Little Girls Made Of", is fairly serious, and gives a nod to the ending of episode six with Gwen moping a bit at the beginning. The sad thing is, by production numbers, "Pier Pressure" should have been aired sixth, and then "Max Out" seventh; as it is, Gwen spends an entire episode happily encouraging her cousin to ask his crush out, and then bantering with Kevin on why he's slow to ask her out, before suddenly snapping back into grief.
Garfield: His 9 Lives goes from standard Garfield humour, to a surreal take on the Garden of Eden story, to a sad story about a pianist's first cat, to a nightmare-inducing scenario involving a lab cat, to a tribute to Krazy Kat. And at the end Garfield meets God. If you think that's bad, try to find the graphic novel it was based on. Most of the stories made it into the animated special, but not the one that ends with Garfield, drawn as a realistic orange tabby that's either driven crazy by time travel or possessed by evil spirits, leaping with fangs bared and claws outstretched right into the face of his owner, an elderly woman. (Who's not even looking at him, and saying "come play with maw maw" right as he's pouncing.)
Transformers Animated does this a lot during the third season. The first two seasons were relatively light-hearted, with most every death being ambiguous. "Transwarped" rolls around and we have Blurr crushed into a cube, Sari nearly killing Bumblebee after accidentally overupgrading herself, and Omega Supreme begging Ratchet to shut him down after he's possessed by Starscream. Then it's on to "Three's A Crowd", featuring the wacky antics of Bulkhead and the Constructicons. Then it's on to "Five Servos of Doom" where Prowl's ninja mentor Master Yoketron dies in Prowl's arms during a flashback.
Speaking of Transformers and mood whiplash between sequels, Beast Wars, despite deep and emotional episodes such as "Code of Hero" and "Transmutate", was generally thought of as light-hearted and humorous. Its sequel series however, Beast Machines, was much darker with an entirely different tone, look, and feel. Even Simon Furmon commented on how dark it was. This led in part to fan backlash.
Speaking of "Code of Hero", we have Dinobot's last conversation where the Maximals are solemnly discussing Dinobot's sacrifice and Rattrap speaks up in a Call Back to a previous conversation they had that episode about where Dinobot stands. Still in pain, he says "upwind of you for preference", putting a smile on Rattrap's face, knowing his best friend won't let his imminent death stop their verbal sparring matches.
This happens a lot with the Bilingual Bonus substitution cipher that is cybertronix. For example, there is one passage in the Transformer equivalent of the bible, quoted in the dialogue as "And a great dragon was cast out onto the earth, and his followers with him", something treated with appropriate religious and prophetic weight. Translating the onscreen text, however, reveals that the sentence continued "two corks, one fork, and a bowl of beans between them".
In Courage the Cowardly Dog, "Last of the Starmakers" tends to go back and forth between the last moments of the life of a space squid, and some silly antics with some Ninjas only marked "1", "2", and "3". It's rather jarring.
The show stuck to this trope since season 5, with episodes such as "Kenny Dies", "Raisins", and "Guitar Queer-O", dealing with the death of a friend, a painful break-up, and the drama between good friends respectively.
Most of the first half of season 15 was lighthearted goofiness, often showing how stupid various characters (or the South Park-verse's inhabitants as total) are. You're Getting Older is a Wham Episode where the group breaks up, Stan's parents divorce, and Stan thinks the whole world sucks... Also Kyle and Cartman seem to be friends now.
Futurama is notorious for sudden mood whiplashes, and for doing it numerous times within an episode, not just the show's infamous tear-jerker endings.
"The Sting" is probably the best example — you could be severely depressed, sniffling, and in agonizing pain as a guilt-consumed Leela descends into madness, her hopes dashed for the THIRD time, yet laugh your ass off as her warped mind imagines the entire crew launching into a broadway-style musical number, complete with flashing lights, and then be knocked into a shivering, sobbing mess by the following scene.
The episode with Fry's dog. The entire episode, you're built up to expect that he'll get his dog back, wacky hijinks ensue, and then Fry discovers that his dog lived for twelve more years after he was frozen, so he had a full life, it's not right to bring him back, and the dog probably wouldn't even remember Fry anyway. Then we discover that the dog spent those twelve years waiting faithfully for Fry to come back, only to die of old age.
Hell, that ending was so sad that the writers ended up retconning it in one of the movies.
Or the episode where Fry is weeping at the revelation of how much his brother loved and missed him... while in the background Bender collects enough skulls for a Mousketeer reunion.
The Late Philip J. Fry has an extremely dramatic Commercial Break Cliffhanger when Fry, trapped at the end of the universe due to a time machine that can only go forwards, discovers the beginning of a message to him on the ground.
One example being the episode "Kid Stuff," which manages it with one line of dialog. After a relatively lighthearted adventure featuring magically pre-teen versions of Wonder Woman, Green Lantern, Superman, and Batman and drawing much humor from the fact that Kid!Batman's attitude hasn't changed a bit, Wonder Woman comments that it was nice being a kid again. Batman responds with, "I haven't been a kid since I was eight years old".
And it's followed almost immediately with the scene of Mordred, a shriveled old man, doomed to age and wither for all eternity, being taken care of by his mother. In contrast to how he was in the episode as a kid, it's kind of a shock.
Robin's constant puns and one-liners can be a bit distracting in serious fights or chases.
It also may have been intentionally invoked with Baby Doll and her rapid switching back and forth between her real voice and her disgustingly cute persona.
Worst of all is probably the second part of the "Feat of Clay" two-part episode - the one in which actor Matt Hagen becomes Clayface. After realizing that he's been turned into a large, blobby clay monster, Hagen screams "I'm not even a man!" and begins sobbing. The very next time we see him, not only has Hagen apparently resigned himself to spending the rest of his life as a freak of nature, he is now gleeful about it, because now he can "morph" himself into various nonthreatening characters, sneak up on people he doesn't like, and kill them.
The Oscar nominated film, Screen Play, starts out as a quiet romantic Japanese tale that seems to end happily, until a jilted character suddenly bursts into the stage and starts killing everyone in sight, starting with the narrator.
Schoolhouse Rock's "The Tale of Mr. Morton" ends in a sweet but undeniably disorienting way, since it goes straight from Mr. Morton wallowing in despair over his inability to ask Pearl out to Pearl proposing to him (I'd pothole that to Fourth Date Marriage, but it's more like Zeroth Date Marriage) and the two of them living Happily Ever After. Even the music does a 180.
The first Star Wars: Clone Wars show, when General Grievous kicks his way into the Chancellor's office to try and kidnap him. The Jedi rush the Chancellor out, leaving the clones behind to stall him in scenes of what is very nearly explicit carnage (only the lack of blood kept it from being truly horrific). Cut to the Jedi waiting for the elevator to arrive, with screams, blaster fire and chainsaw sounds coming from the office. And then one of the Jedi reaches out and pushes the elevator call button 6 times to make it get there faster.
Megas XLR begins with a Humongous Mecha space battle presented in the tried and true Space Opera style. This lasts for over seven minutes as female lead Kiva Andru runs off with the enemy's Super Prototype and tries to send it back in time a few years so it can change the desperate last stand in favor of humanity. The alien forces attack, and things go wrong. After the title and commercial break, cut to two Clerks-style slackers from New Jersey...
"The Boys of Bummer", has Bart being hated by everyone in town and being Driven to Suicide because of it in one of the most disturbing plots in the show's history. It alternated between a light-hearted subplot of Homer becoming a mattress salesman and accidentally trading his with the Lovejoys.
Homer does it to himself when in the video store, alternating between looking at two screens, one showing a comedy and the other a Tear Jerker.
In "Homer the Moe", Moe's professor commits suicide by walking into the campus lake on-screen. Cut to Homer singing a chirpy ditty - "I'm-a-walking down the street, going to open Moe's bar…"
In "Treehouse of Horror III," Homer is in a store selling forbidden objects and frozen yogurt (referred to as "frogurt"), leading to a back-and-forth containing this trope between Homer and the shopkeeper.
A scene in the first act of "Brother From the Same Planet" has Homer dozing off while taking a bath and dreaming about being very late to pick up Bart from soccer practice (which, in fact, he is). The dream shows him driving in a wild panic up to the field, only to find a skeleton in soccer clothes with Bart's famous "hair-spikes" at the top of its skull; apparently Homer kept Bart waiting so long that Bart starved to death. Homer gathers up the corpse, screams, and sobs - which prompts him to wake up, leap out of the bathtub, and frantically run out to his car dripping wet and completely naked (causing Ned Flanders to remark: "Homie, I see your doodle!"). Then, in the next scene, the "serious-to-silly" shift reverses itself with a very upset Bart getting in the car as Homer tries to hand him a hot-fudge sundae (which he bought to apologize), only for Homer to spill the sundae right on top of Bart's head. Homer then does his best to make up with his son as Bart just sits there glowering straight ahead, the ice cream and hot fudge dripping down his face and neck, getting angrier and angrier. The scene ends with Homer urging: "How about a hug?" Bart finally glares over at his father...and imagines him as an emaciated, eyeless zombie. Pretty jarring, but certainly keeping up the Black Comedy overtones of the series's earlier seasons.
And after that, we cut to Bart at home watching an episode of Tuesday Night Live hosted by Krusty the Clown.
"Man's Best Friend" starts out rather cheerfully with happy Raymond Scott-like music played in the background... and then very unexpectedly cuts into a loud dramatic sting and a sinister-looking "Starring George Liquor" card.
There's a literal in-universe example caused by a device called "the happy helmet". It's an invention of Stimpy's that can change moods from any sort of anger or sadness into absolute happiness with varying levels of intensivity.
"Sven Hoek" features Ren acting insanely angry when describing how he's going to hurt Sven and Stimpy before stating perfectly normally that he has to pee.
The two-parter where Stewie kills Lois. For the first 8 minutes, it's the usual post-cancellation FG humor, and then, Stewie sneaks aboard onto the cruise ship and shoots Lois, who appears to have died as Stewie intended, and fell from the ship into the ocean. Joe had to call off the 6-day search for her, and a year has passed since. Brian finds out that Stewie killed Lois, suspicion from Quagmire, Cleveland, and Joe falls on Peter when he recently takes a life-insurance policy on her, Stewie throws away his gun and drawing of himself killing Lois, and Peter's friends find the evidence and believe that Peter did it, leading to Peter's testimony in court. He was found guilty, but then, Lois shows up, alive, and tells everyone that Stewie killed her.
Part 2 reveals how Lois came back to Quahog. She was saved by a Merman, which isn't the kind of what you had in mind. Lois lost her memory and worked at a summer camp for fat kids, preventing them from eating each other. She then meets a man named Derek, who was a White Supremacist. At a meeting, Lois' opinion gets her a bottle to the head, restoring her memories. Stewie then holds his own family hostage, kills Cleveland, and forces Brian at gun point to do as he says and later on, drive him to the CIA, where a Crossover with American Dad! ensues, and then Stewie becomes the tyrannical president of America, in which he makes up absurd laws (i.e. banning direct-to-video Disney sequels and throwing apples at Peter). Lois can't take it anymore and plans to take down Stewie on her own. As Lois and Stewie took each other on, the fight ends with Peter killing him, but luckily, it was all just a simulation.
Despite how dark the two-parter was, there were some funny stuff between all of the drama, even though most of the funny stuff were cutaway gags.
In "Screams of Silence: The Story of Brenda Q", the episode starts off with its usual shenanigans until it slowly shows off a very realistic spouse abuse between Quagmire's sister and her boyfriend. Everyone gets uncomfortable and they even try to convince Quagmire's sister to dump her boyfriend, but she refuses due to being engaged to him. Quagmire and Peter then plot to kill the boyfriend, but Joe refused to get involved since it would be against the law until he witnesses Quagmire's sister getting beaten, causing Joe to darkly say "Let's waste this dick." The entire episode is very dark and grim with very little humor compared to the other episodes and it's rather jarring to see spouse abuse used realistically when the entire series showed the Griffin family abusing each other for shits and giggles and appear to be fine afterwards.
ReBoot had an episode with alternating scenes of Dot and Bob's wedding preparations and Glitch-Bob slowly dying in the Supercomputer. He got better, but then it got a LOT worse.
There was a cut-away gag once about TV announcers who "lull you into a false sense of security" by alternating announcements of zany comedies with those of dark, disturbing dramas.
Animaniacs. It could go from a show in which cute cartoon characters run around eating sweets or singing nonsense songs to a show in which cute cartoon characters look for a home or get taken into care in THE SAME EPISODE. And it's AWESOME.
Happens barely two minutes into the My Little Pony pilot. One moment the Ponies are frolicking around, being Moe Moe and all other sorts of unimaginable adorable, and then demonic dragons come flying out of the sky complete with a thunder storm and kidnap several of the ponies to become slaves.. Yup. It happens a few other times in the pilot, too; One moment they're singing, and the next, something horrific happens.
The ending of it is the reverse of the beginning. You get an epic fight sequence with Tirek, an extremely dark and menacing villain, ending with the heroes blasting him apart and vaporizing him, after which it immediately shifts to a lighter atmosphere complete with the My Little Pony theme.
The first My Little Pony special featured killer dragons, an Omnicidal Maniac villain and very little fluff, and was mostly action based. The next special is considerably more sweet—though still dark.
Every time there's a two-part story, the first part ends in a dark cliffhanger... followed by the happier ending tune. It's almost a Running Gag, though there's no evidence it's deliberate.
The series premiere ends with a cliffhanger as the Big Bad brings about eternal night, then suddenly the happy ending tune kicks in.
The Season 2 premiere takes it Up to Eleven and beyond in both directions. Start with an argument between the Cutie Mark Crusaders. Move on to cotton-candy clouds raining chocolate milk and corn popping off its stalks. Then we have Discord turning all the mane cast (except Twilight) into their polar opposites and tricking them into losing his challenge to find the Elements of Harmony. Just as he gets ready to unleash total chaos on Equestria, cue the happy ending tune.
The Season 2 finale — is there an Up To Thirteen? Because it gives us Twilight Sparkle, emotionally crushed, allows her a split-second Hope Spot — and then, to all appearances, 'banished to the Underworld in a circle of green hellfire'. Cue "Doot doo doo doot doo, Myyyy Little Pony". If they hadn't shown the two parts back to back, the bronies would have rioted.
The first part of the season four two-parter finale ends with Twilight learning that Discord has joined forces with Tirek, and all of the princesses need to transfer their magic to her to keep it away from Tirek, otherwise he'll steal it and rule everything. Cue the upbeat credit music!
Done in-story when Twilight Sparkle realizes her "friends" aren't interested in helping her stop the Big Bad.
Twilight:(dejected) I never thought it would happen. My friends... (pause) Twilight:(angry) ...have turned into COMPLETE JERKS!
This becomes more And-I-Must-Scream-worthy when taken into consideration that petrified characters are still cognizant of their surroundings.
In "Owl's Well That Ends Well", the transition from Twilight gently praising Spike as he sleeps to angrily confronting him about her burnt astronomy book is very sudden and shocking.
The song "Becoming Popular (The Pony Everypony Should Know)" from the episode Sweet and Elite is a very upbeat tune about Rarity's happiness at being accepted into high society...until the last bit, when it suddenly turns very somber and somewhat saddening as she realises she is just too exhausted to complete her friend's birthday dress in time.
Something similar happens in "Pinkie Pride". Cheese Sandwich's "I Am" Song, which is every bit as silly and upbeat as you'd expect a character voiced by Weird Al Yankovic to sing, ends on an incredibly solemn note as the viewpoint shifts to Pinkie Pie feeling depressed and unwanted.
The episode "Baby Cakes". One somewhat short scene in the second half of it could be considered a shout out to horror movies in general, what with creepy children laughter and SOMETHING CRAWLING ON THE CEILING! Oh, did I mention the plot is Pinkie Pie babysitting children?
A Mood Rollercoaster in Twilight's Kingdom Part 2— between scenes of Tirek conquering Canterlot, then heading to Ponyville to drain Twilight's friends of their magic and invoking You Have Outlived Your Usefulness on Discord, we're treated to mostly comical scenes of Twilight trying to get her new powers under control and botching her spells.
A cartoon simply called The Snow Man (no, not that one) starts out with sickeningly sweet Disneyesque cheeriness and dancing. Then suddenly, the snowman comes to life with its blank snow face melting into a monster face and it goes on a rampage trying to kill everyone.
The episode "Holly Jolly Secrets". For the most part, it's a holiday episode where Finn and Jake find some of the Ice King's abandoned video tapes and decide to decipher them for "evil secrets". Many of the tapes are of the Ice King playing with his penguins, attempting to work out, and making fake news interviews with captured princesses. Then, when the Ice King barges in to reclaim his tapes, Finn quickly puts the last video in. It's a video of a human professor telling the camera how he purchased a mysterious crown from a Scandinavian merchant. This crown gave him horrific visions when he put it on, frightening away his fiancée. As the clips progress, the professor becomes more and more resembling of the Ice King, his mental state deteriorating until he only wishes to find "his princess again". Finn and Jake's reactions are the same as the audience's.
Ice King:(sobbing) Now you know my secret... I used to wear glasses!
The second installment of the Ice King's backstory, 'I Remember You', begins as a lighthearted story about the Ice King trying to record a song with Marceline. Cue a couple Odd Couple gags, and she relents. After a few bars, the Ice King begins to sob wildly, pushes Marceline, and runs away to hide on top of the refrigerator. At this point, it becomes a straight up Tear Jerker. It could be especially jarring to watch the episode the second time through with the knowledge that the Ice King :has crown-induced Alzheimer's. Many of his wacky actions in this episode give neck-breaking mood whiplash to people who can recognize Alzheimer's symptoms once they have a general idea of his condition. Word of God has said this was intentional. The show's Tear Jerker section has more details in case you want more Mood Whiplash.
When Lemongrab is discovered watching the candy people while they sleep, he slinks out through a window backwards, his voice emotionally tortured as he states "No one understands, I am alone, and you made me like this." The next scene is Lemongrab running away from the castle while tearing his clothes off screaming "You made me!" It's somehow heartrending and simultaneously hilarious.
"Jake the Dog" goes from Alternate!Finn being corrupted by the Ice King's crown and Alternate!Jake becoming the Lich to the regular Jake happily hanging out with Prismo and Cosmic Owl.
Mood whiplash occasionally happens in Wakfu. The biggest offender would have to be the 15th episode of season one. We close on "à suivre" (French for "to be continued"), our heroes apparently engulfed in a dragon's fire breath. Then we get the episode's Couch Gag, and a silly little drum ditty the gang plays on a barrel to try to wake Ruel inside.
Chuck Jones' Feed the Kitty is one giant Mood Whiplash after Pussyfoot falls into the batter and Marc Anthony thinks she is being made into cookies.
Madagascar 3: Amidst all the colorful wackiness there's a quiet drama scene with Alex the lion and Vitaly the tiger. In the middle of it, for no apparent reason, the two cats have a brief slap fight over a ball of yarn.
In the second episode of Goof Troop "Good Neighbor Goof", there is a shift from comedy (Pete's failed attempts to bust Goofy's house) to pathos (first instance of PJ's servitude) back to comedy (the omelette and the hedge-trimmer) then to peril (Max and PJ flying through the air and almost drowning) which leads to a heartwarming bonding moment (Max and PJ's friendship blooms) and then from dramatic tension (PJ's getting caught) to comedy again (PJ forgets he doesn't have a balcony) then back to dramatic tension mixed with pathos (Pete forbids him from seeing Max) then even harsher pathos (PJ's super-depressing line) which itself leads to more comedy (the luau scene) then pathos (Pete giving PJ the last rule) and then comedy again (Goofy giving Max the last rule) and then dramatic tension mixed with comedy (Max's plan to save the friendship) and then finally a heartwarming bonding moment ("Mission accomplished" and family portrait). This occurs because this episode follows all the characters' focus episode formulas mixed together.
Motorcity: Due to the wacked out order that the episodes were being aired, we get the hilarious "Threat Level Texas" and then next week we got "Vega" which has a whole lot of "Oh Crap!" moments to put it extremely lightly.
Scooby-Doo! Mystery Incorporated: Switches from dark to comical, to melodramatic, every so often. The Devouring for example, has a climax where Scooby and Shaggy get incredibly obese and beat the monster at a sumo contest. She's rolled away, with one of the recurring characters, Dr. Spartan, repairing his relationship with his wife soon after. Immediately after that it cuts to the villains with Pericles having put mutated cobra venom into Mr. E's spine to poison and torture him if he gets out of line.
The Adventures of Jimmy Neutron: Boy Genius: In the episode "The Great Egg Heist", Professor Calamitous uses a robot suit of a a Chinese woman to convince Jimmy and the rest of his gang to steal a jade egg from the museum. When they give it to him, Jimmy points out that his friends helped him and Calamitous comments in the suit's voice "Then I suppose it is only fitting that your friends" then adds "Share in your ultimate downfall" in his actual voice.
The Legend of the Titanic: The group of mice try to fix the telegraph by having one of the mice use their mustache to connect the wires with hilarious results of the signal going through but then he dies.
The "What Do They Fear?" Episode of DuckTales "Nothing To Fear" starts with Magica's spell making everyone hallucinate pretty silly fears that are all played for laughs (a limousine and a banana turning into monsters, the boys' video game's villain coming to life, Scrooge being chased by bill collectors). Then, out of nowhere, it gives the boys (who, keep in mind, have already lost their parents and just had an uncle leave them to serve in the Navy) a vision of Uncle Scrooge telling them he never wanted them and can't stand having them around, and Scrooge hallucinates the boys telling him they never liked anything about him except his money. All four of them are in tears before they finally realize what's going on. No wonder it remains one of the most unforgettable episodes of the series!
Steven Universe, being for the most part a light-hearted comedy, has some shockingly dark twists despite only being about two thirds through its first season. The most notable ones so far are:
The episode "So Many Birthdays", in which the first half focuses on Steven trying (and failing) to teach the Crystal Gems about birthdays parties, and the second half about Steven becoming depressed and accidentally aging himself to an old man with his powers. The climax has him almost kill himself from old age while the Gems nearly get completely broken trying to save him.
"Steven The Swordfighter", where Steven is amazed by Pearl's sword fighting skills and tries to get her to teach him how. Moments later, he unintentionally distracts her while she's sparring against a hologram of herself, causing her to get stabbed through the gut and explode into smoke, leaving only her gemstone behind. Thankfully, she's not actually dead and she comes back at the end of the episode, but as a part of another Mood Whiplash, right after Steven almost gets murdered by the same hologram in a dark room.