"Christmas Time in Hell" is a joyous song with its lyrics actually matching the tune... but it's a song that sings about how the Damned get the day off from being horribly tortured.
In the episode "The Death Camp of Tolerance," a gerbil named Lemmiwinks is forced to crawl up Mr. Slave's ass, and he (Lemmiwinks) must traverse Mr. Slave's entire digestive system and crawl out the mouth or else he will die. Amusingly, this entire disgusting sequence is described in a song with a merry, adventure-y tune.
South Park: Bigger, Longer & Uncut is built almost entirely on this trope and plays with them:
"Up There": A rousing Broadway showtune about loneliness and wanting to get out of a bad place. Sung by Satan. A Satan who is is not a complete monster.
"La Resistance": "They'll cut your dick in half/ and serve it to a pig./ And though it hurts you'll laugh,/ and dance a dickless jig/ for that's the way it goes/ in war your shat upon/ though you die, La Resistance lives on." Sung by a choir of eight year olds. Eight year olds who usually have IQs higher than their parents but with just as questionable moral compasses.
"Blame Canada": A rousing march about evading personal responsibility to the extent of going to war with Canada, a country that seems to go out of its way to be America's friend. The song, however, is a satire on American tendency to scapegoat others.
In one episode of The Flintstones, Pebbles and Bam Bam are found singing what sounds like an upbeat, cheery song about how "Smilers never lose, and frowners never win." Do you know why frowners never win? Because THE DEVIL WILL GET YOU IF YOU FROWN.
The Ren & Stimpy Show has the "Happy Happy Joy Joy Song". Although the song itself is a deliberately insipid — though insanely catchy — song about being happy, it's the increasingly insane rantings of Stinky Wizzleteats (the singer) between verses that bring some dissonance. "I told you I'd shoot, but you didn't believe me! Why didn't you believe me?!" (The reason is that most of these lines are quotes or paraphrases of Burl Ives' character from The Big Country, but of course younger viewers — especially kids — can't be expected to catch the references.)
One Arthur episode has Art Garfunkel act as a one-man Greek Chorus to the characters' actions and feelings. This includes a part where he sings a lively song about Buster being "a sad, sad bunny." Buster then broke the fourth wall and demanded Art Garfunkel sing a more melancholy version.
The first verse of the Incredible Hulk's segment of the Grantray-Lawrence Marvel Superheroes show of the mid 1960s:
In "Norm Unleashed", Norm the Robot Man brings his own cheerful song about conquering the Tri-State area with an array of deadly, built-in "Weaponry".
If power's on your shopping list Then use the elbow and the fist Hum along until they get the gist Just make an example of Representative sample of And most of them will not be missed!
Candace sings a song called "Give Up" in "Last Train to Bustville". It's a cheerful, upbeat anthem about... giving up. It Makes Sense in Context, since what she's giving up is her obsession with busting her brothers.
"Little Brothers" from Phineas and Ferb is sung to an extremely sweet heartwarming tune, complete with an adorable through-the-years montage of Candace's relationship with her brothers. Then, you get to the silly chorus.
You will always be my little brothers, Cause you're younger, we're related, And you're boys.
The Adventures of Super Mario Bros. 3 gives us "It's a Dog's Life" from "Life's Ruff". The lively and catchy song is about...Luigi and King Windbag wanting to be human again after Hip and Hop turned them into dogs.
Futurama has a cheerful reggae song about being a bureaucrat in "How Hermes Requisitioned His Groove Back".
To say nothing of the Xmas carol, "Santa Claus Is Gunning You Down".
In an episode of The Critic, the national anthem of an unnamed country sounds like a repeated chant of "pee-pee, pee-pee, pee-pee, poopy", but has a rather different meaning.
Tim Burton is a master of mixing the macabre and the lighthearted, so it's no surprise that the music in his movies are the same. The best example is "Remains Of The Day" from Corpse Bride, a swinging jazzy tune about death and murder. Even while you're tapping your feet to the beat, you probably don't miss the extremely dark chorus:
"Die, die, we all pass away, but don't wear a frown, cause it's really ok! You might try to hide, and you might try to pray, but we all end up the remains of the day!"
"The World's Greatest Criminal Mind", from The Great Mouse Detective, is one of Disney's cheeriest villain songs. The most disturbing lyrics?
Even Meaner? You mean it? Worse than the widows and orphans you drowned?
Hoodwinked! crosses it over with Soundtrack Dissonance in a Just Between You and Me. After Red's fight with Boingo in the tram terminal, he orders Dolph to tie her up. She says, "You're crazy!" and he replies "Maybe, but I'm top of the woods now, baby!" So he sings "Top of the Woods", an upbeat song with lyrics about oppression, getting children addicted to goodies, and becoming a ruthless dictator, like:
"When you're hopping on down the bunny trail, the critters all seem to look down You're fuzzy and small Your ears are too tall And goodies make the woods go round"
"Now I'm not a pig But you gotta think big when you're competing with the girl in the hood So you won't be a fan of my evil plan, but I'm gonna be top of the woods!"
"When your only desire is to dominate the land of the wolves and the squirrels You've got to think with a open mind and learn to detest little girls And everyone knows at the end of a show the villain puts his plan into words Except there won't be a rescue before the credits roll cause I'm gonna be top of the woods!"
"Now the kids will be packed with my BoingoSnax Construction begins in a day And all of the bears will be ruled by the hare As I maniacally plot from my evil lair!" [cue evil laugh]
The Island of Misfit Toys segment from Rudolph the Red-Nosed Reindeer starts with a song about the toys being unloved and missing out on the joys of Christmas, when the song itself sounds very cheerful.
"L'il Ark Angel" from Cats Don't Dance starts with Darla singing about the world being destroyed in a flood and people and animals drowning in exactly the same cheerful tone she later sings about the various animals she's rescuing. If you hadn't already realized she'd be the Big Bad of the film from the foreshadowing in the intro, it's hard to miss it after that.
Some of the Silly Songs With Larry invoke this. From an 80s love ballad...about cheeseburgers to a tango...about manatees, the team purposely make the music sound completely authentic to the genre while keeping the silly lyrics.
"Batty Rap" from FernGully: The Last Rainforest. It has a fast and springy beat and tune.....with the lyrics being about how Batty was used in animal testing laboratory, with strong implications that he was conscious throughout all the processes. Due to its 'adult' nature, quite a bit of the song was cut from the film, but was left in on the CD.
"The Eye makeup, when inserted rectally, has some effect...
Remove the brain cap...
If you notice, by dipping the bat in a series of paints...
After 600 packs of cigarettes, the animals seem to exhibit some carcinogenic tendencies..."
The children's movie The Brave Little Toaster contains a song near its end which the other wiki sums up perfectly: "Worthless is sung by the junkyard's broken down cars, each singing a few verses about their life before being smashed and killed by the compactor." However, they fail to mention the upbeat music it's sung to.
"Christmastime Is Here" from A Charlie Brown Christmas. It has lyrics that describe how wonderful Christmas is ("Fun for all that children call their favorite time of year") but has a very slow, almost melancholy feel to it. This makes it memorable.
"Won't You Come over to My House?", best known from the famous short One Froggy Evening. If your memory's a bit hazy, here's the cartoon (songs only), and here are the full lyrics.
This is pretty much the entire gimmick of Dethklok on Metalocalypse, as they render everything, from the blues to a jingle for a coffee shop to a birthday song, as over-the-top death metal.
The song "The Violin", by Brian Dewan, is included on the album Where In The World Is Carmen Sandiego?, notably a kid's show. It is set to decidedly upbeat, Irish-sounding music. The song's lyrics discuss a kid who is constantly trying to break away from his controlling parents' desire to make him learn the violin, getting snubbed by his crush for someone who does, and then ultimately drowning in a shipwreck. It's a children's album, fun for the whole family!
The titular song by Rockapella could qualify, as a peppy upbeat number about an impossible-to-catch criminal and her various misdeeds.
Music by Jody Gray are great examples of this trope. Both Arthur's Missing Pal and Clifford's Really Big Movie feature upbeat music... with downer lyrics about the protagonist's lost dog?!? In the latter, the opposite also occurs on a tribute CD: the owner of said big red dog sings upbeat lyrics about her dog to a bitter-sounding tune.
The song "Mother Knows Best" in Tangled is a cheerful, bouncy song where Gothel terrifies Rapunzel by listing off all the "scary and dangerous" things in the outside world and how all of them will happen to Rapunzel if she steps out of the tower. Throughout the song, Gothel is intentionally emotionally abusing Rapunzel by playing with her fears to make her seem like she's the only one in the cruel world Rapunzel could trust.
If we're on the island of unwanted toys, we'll miss all the fun with the girls and the boys...
"The Ballad of Magellan" from Animaniacs, a rather lively and happy-sounding song about Magellan's famous voyage - the one that ended in his death. The song is far more lively than the lyrics, tune, and story (which is actually historically accurate) suggest.
Rainbow Dash: Three months of winter coolness, and awesome holidays
Pinkie Pie: We've kept our hoovsies warm at home, time off from work to play
Applejack: But the food we've stored is runnin' out, and we can't grow in this cold
Rarity: And even though I love my boots, this fashion's getting old...
In "The Singin' Kid" on PB&J Otter, there's Jelly Otter singing about friends and family keep her strong and being true to herself at the same time she lets fame go to her head in "The Singin' Kid."
"Let It Go" from Frozen, an uplifting-sounding song by Elsa about finally accepting her powers... which is also about choosing to live a life in isolation and cut herself off from the world. Ironically enough that's inverted on a meta-level, seeing as by many people it's viewed as an empowerment anthem and has actually encouraged many, which is arguably the opposite of what some dissonance may suggest it means for Elsa. Also of note is that it was originally meant to be a Villain Song before the story was changed, and the song led people to treat it as... well, the exact opposite. Irony at its finest.
One episode of Tiny Toon Adventures did a music video of "Particle Man" by They Might Be Giants (which the band approved of) with an odd twist. Although the lyrics were not changed, Universe Man was just as mean to Particle Man (played by Plucky) as Triangle Man was, despite what the lyrics said. You can see it here.