While these animated worlds may appear to be filled with whimsical and colorful adventures, a closer examination often uncovers a well of despair, or even dark secrets, lurking beneath the surface. Such complexity is expected in adult animated series. Consider Rick Sanchez from “Rick and Morty,” a character whose tragic backstory reveals that he witnessed the murder of his family by Prime Dimension Rick, adding layers to his character.

However, animation’s darker narratives aren’t reserved exclusively for mature audiences. Behind the bright watercolor landscapes of “Adventure Time’s” Land of Ooo, the sinister past of Bill Cipher in “Gravity Falls,” and even within the enchanting universe of “My Little Pony,” lie 12 cartoon character backstories so unsettling that they might change how you view these shows.

Take the Ice King from “Adventure Time,” known for his eerie obsession with princesses and his glittering crown. In the episode “Holly Jolly Secrets,” viewers discover that he was once Simon Petrikov, a kind-hearted antiquarian, voiced by Tom Kenny. Although he wasn’t superstitious, Simon’s fate was sealed when he donned the magical and cursed crown, leading to a mental fracture.

It might seem like the only thing that Ice King — the creepy, princess-kidnapping “Adventure Time” troublemaker — has going for him is that gorgeous ruby-encrusted bling atop his noggin. But in “Holly Jolly Secrets,” we learn he’s not just a leering creep of his own accord when it’s revealed that Ice King was once a nice, normal antiquarian named Simon Petrikov (Tom Kenny). Despite not being one for superstition himself, Simon’s brain was predestined to fracture beyond all sense the first time he tried on that sparkly (and incidentally, deeply cursed) headwear just for the heck of it.

Not long after trying on the crown, Simon began to experience short lapses in sanity and bouts of amnesia, eventually leading to full-blown insanity and his transition into the Ice King, as well as separation from fiancée Betty Grof (Lena Dunham). In the midst of that transition, Simon watched the world fall to the Mushroom Wars and adopted the orphaned Marceline, knowing all the while he would eventually forget her (and potentially harm her, as well).

For the next thousand years, Ice King lived a lonely life encapsulated in madness with no recollection of who he once was nor remorse for what he was becoming, making Ice King’s story the most tragic in “Adventure Time.” But as Ice King himself says in “I Remember You,” “Ladies are drawn to guys with tortured pasts — and I’ve got a way tortured past (I think).”

Running for four seasons on Cartoon Network around the turn of the millennium was the completely unhinged animated horror series “Courage the Cowardly Dog,” which saw its ironically named protagonist Courage (Marty Grabstein) regularly facing off with all sorts of surreal horror and sci-fi tropes. Throughout the show’s run, we see him living with the sweet Muriel Bagge (Thea White) and her cantankerous husband Eustace (Lionel Wilson and Arthur Anderson). But in “Remembrance of Courage Past,” we learn the truly disturbing backstory that leads to Muriel adopting Courage as a terrified puppy she found and rescued from an alley one day.

Through Courage’s flashbacks, we see a tiny, diapered Courage running around in what looks like a dog pound, surrounded by trapped dogs in cages. Using his tongue to open the door, Courage the pup manages to locate his parents just as the Cruel Veterinarian (George Hall) is launching them to space in a rocket, all part of his mad science experiment aimed at creating a superpowered “Space Dog.” He manages to escape through a trash chute just in time to watch his parents launch into space moments before Muriel finds the terrified pup, naming him “Courage.” Years later, when Courage sends the Veterinarian to space, we learn his parents have been trapped there ever since, presumably for decades, with all the other dogs from the experiment.

The “Steven Universe” franchise — which comprises two complete animated shows (“Steven Universe” and “Steven Universe: Future”) and a movie (“Steven Universe: The Movie”) — is full of stories about growth, relationships, and finding one’s way through trauma. Pretty much everyone in this franchise has a complicated and at least somewhat tragic or disturbing backstory that either hinges on or relates to generational trauma left over from the Gem War, a rebellion against the Gem Homeworld’s plan to take over the already inhabited Earth. But almost no character in the franchise has a backstory as disturbing and existentially frightening as the original or “Mother” Centipeetle, once known as Nephrite.

We first learn of Centipeetles in “Gem Glow,” when a whole gaggle of Centipeetles invade Steven’s room. Although Steven (Zach Callison) initially finds the oversized bug-like critters “awesome” and “really cool,” their unruly behavior and corrosive acid they spit makes them less-than-desirable pets — especially when the monstrous-sized Mother arrives. Eventually, it’s revealed she is a corrupted Nephrite (Aparna Nancherla), a squadron leader who was reduced to a mindless, animalistic existence at the end of the war by the Diamonds’ attack. For thousands of years, Nephrite is forced to wander the Earth in this state until Steven bubbles her. But even when Steven attempts to heal her, he can’t finish the job, leaving her semi-corrupted until he finally rejoins with the Diamonds in “Change Your Mind.”

Far more than just a colorful Disney cartoon about preteen twins Dipper (Jason Ritter) and Mabel Pines (Kristen Schaal) bumming around its titular Pacific Northwest paranormal hotspot, the 2012 animated mystery “Gravity Falls” weaves an intricate puzzle full of secrets hidden deep inside its triangle-shaped iceberg of lore. And at the center of that iceberg is one Bill Cipher (Alex Hirsch), a top hat-wearing, malevolent, interdimensional demon summoned that looks like a cuter version of the Eye of Providence. Between the series and its lore-heavy books, we get to learn all about his dark and disturbing history — one befitting of an ageless demon. As revealed in “Gravity Falls: Journal 3,” Bill is a genocidal monster.

Bill’s story begins more than a trillion years before he was summoned by a relative of the Pines. He was born in the two-dimensional Flatland-style realm of Euclydia, a cute little triangle adored so much by the Euclydians that they declared his birthday a holiday. When his all-seeing eye let him perceive the third dimension, one that even to speak of was completely outlawed in his world, Bill burned his entire reality out of existence, killing everyone who ever knew or loved him and moving into the Nightmare Realm between worlds. So traumatized by the horror of what he did, Bill dissociates and blacks out anytime he almost remembers it.

Based on the charming French children’s book series by Jean de Brunhoff, the animated series “Babar” is the very embodiment of wholesomeness. The series follows the family of King Babar (Gordon Pinsent), the African elephant who rules over Celesteville, as Babar recalls events and experiences from his childhood and early monarchy. And although life in Celesteville appears to be mostly ball games, picnics, and pastel-colored parlors, Babar’s childhood was actually pretty horrific.

As recounted in “Babar’s First Step,” the future king was lovingly welcomed into his elephant herd as a babe, where his mother allowed him to name himself Babar at only a few hours old. His life is idyllic until one day, while playing with his future queen in the local watering hole, the herd is attacked by a hunter. While running toward the jungle for safety, Babar’s mother is killed by the hunter’s rifle, leaving young Babar to heartbreakingly run about while calling her name until the herd brings him to her corpse.

Originally conceived as the star of adorable short cartoons “The Friendly Ghost,” shown in theaters from 1945 to 1959, Casper the Friendly Ghost is another one of those awfully wholesome cartoon characters with a deeply disturbing backstory. But in Casper’s case, it wasn’t always that way.

As portrayed in the original series and its various sequels and comics, Casper is a bubble-headed childlike spirit shaped a bit like a kid wearing a sheet for a Halloween costume. But unlike other, scarier spirits, Casper is just a silly little guy who wants to have a good time and make a few friends along the way.

While earlier stories simply avoid the topic of how he got that way, the 1995 film adaptation “Casper,” starring a very young Christina Ricci alongside Devon Sawa as Casper, finally gives the little ghost boy a seriously heartbreaking backstory. Although he’s (probably gratefully) forgotten how it happened over the years, Casper recalls his death after young Kat (Ricci) decides to clean up Casper’s old playroom. In the devastatingly emotional scene, Casper recalls how he took his wooden sled out to play one day, ultimately leading to his death of pneumonia. It’s distressing enough, until you consider how time made him forgot his life and family, becoming an amnesiac ghost and permanent child with no sense of identity beyond his name.

Originally airing on YouTube and later Netflix, the web series “Bee and PuppyCat” is one of the sweetest, loveliest, and frequently trippiest cartoons of its era. The pastel-hued, surrealist sci-fi fantasy series follows the young adult Bee (Allyn Rachel) and her pet PuppyCat (voiced by the Vocaloid Oliver) as Bee takes on various gig work assigned by an interplanetary temp agency.

Bee appears to love caring for PuppyCat, a smallish, bipedal white doglike creature with the features of a cat, who she adopted after it appeared in a portal on her way home from getting fired for sleeping on the job. In “Donut,” we learn Bee, who has an extreme dislike of water and never seems to age, is actually a robot, which is already pretty disturbing. But it’s PuppyCat’s story, as revealed through his lullaby fairy tale, that remains the darkest in the series.

In the lullaby, PuppyCat sings of a Space Outlaw, later revealed to be himself before transformation. After falling in love with the Space King’s Daughter, the Outlaw was turned into a “monster” by the magic meant to capture him, separating the lovers while permanently trapping PuppyCat in his pet body.

Much like “Gravity Falls,” “The Owl House” is another one of those high-quality Disney animated series with some fairly complicated worldbuilding behind it. The comedy fantasy horror series follows the geeky Luz Noceda (Sarah-Nicole Robles), a sweet, nerdy Afro-Latina in her early teen years, after she follows an owl “Alice in Wonderland”-style to a magical land called the Boiling Isles, made from the body of a Titan. After befriending a witch named Eda Clawthorne (Wendie Malick) and her demon roommate named King (Alex Hirsch), Luz straight up abandons the regular world to hang out with the Clawthorne family at their “Owl House.”

What makes King’s backstory so utterly horrifying, though, is his relationship to the Boiling Isles. That’s because the Titan they’re all living on actually turns out to be King’s parent “Papa Titan,” a fact revealed in the series finale “Watching and Dreaming.” That’s right: After getting lied to about his nature his entire life by Eda, King eventually finds out he’s been living on top of his dead parent’s corpse all along. Now that’s dark.

Cartoon Network’s limited dark fantasy series “Over the Garden Wall” tells a haunting but charming tale of half-brothers Wirt (Elijah Wood) and Greg (Collin Dean) as they end up lost in a bleak enchanted forest called the Unknown, trying to find their way home. Along the way, they meet all sorts of strange, dark, and fascinating characters like the pumpkin-wearing skeletons of “Hard Times at the Huskin’ Bee,” the animal students of “Schooltown Follies,” a friendly bluebird named Beatrice (Melanie Lynskey), and an initially helpful Woodsman (Christopher Lloyd), who warns the boys about the Beast, a monstrous figure who roams the forest.

We see the Woodsman again as the brothers venture further into the dark forest, eventually coming to learn the dark and disturbing tale of exactly who the man is and how he got there. After the Woodsman saw his wife die from an animal wound, the Beast conned him into believing his daughter’s soul was in a lantern and would stay alive as long as it remained lit. But in one of darker moments in any animated series, we learn it only used one type of fuel: oil from the Edelwood tree. We eventually learn he was tricked by the Beast, forced into luring young children into the forest to harvest trees that grow from their souls. Fortunately, he eventually rejects the Beast, blowing out the flame and reuniting with his lost daughter before it’s all over.

The network-friendly animated sitcom “King of the Hill” tends to keep things pretty lighthearted. A slice-of-life series about the Hill family of Arlen, Texas, “King of the Hill” mainly revolves around propane salesman patriarch Hank Hill (Mike Judge), his substitute teacher wife Peggy (Kathy Najimy), their tween son Bobby (Pamela Adlon), and their niece Luanne (Brittany Murphy). But the series has plenty of time to highlight the Hill family’s neighbors, and the real backstory of their neighbor Bill Dauterive (Stephen Root) is just a little disturbing.

During the series, Bill is portrayed as a clinically depressed divorcé, an overweight middle-aged transplanted Louisianan with even less self-esteem than hair. As a child, Bill was beaten and forced to wear dresses by his sadistic father. Despite his abusive childhood, Bill still went on to become a star athlete with a bright future ahead of him as a U.S. Army tanker; however, he then married Lenore (Ellen Barkin), who destroyed almost every last remaining shred of dignity he had.

It’s almost hard to feel sorry for the Pokémon Meowth, a Normal-type Pokémon with a Brooklyn accent and the personality of a criminal mastermind. The fact that he hangs around Team Rocket, cooking up their little devious schemes, doesn’t really help his case much. But one thing that might tip the scales ever-so-slightly in his favor is the tragic backstory he lets slip in the “Pokémon” animated series episode “Go West, Young Meowth.” And what makes it truly disturbing is the very adult realization that it was a life of hardship and poverty that turned him to a life of crime.

Leaning against a wall, a trench coat-clad Meowth tells Team Rocket, “There are things you don’t know about me; things I like to keep private.” While standing before a Hollywood hamburger and hot dog stand, Meowth (Maddie Blaustein) recalls never knowing a family as a child and experiencing hunger as an unwanted stray, even crying himself to sleep. But things changed when he hitched a ride to Hollywood, eventually joining up with a pack of hooligan street Meowths. But it was only after falling for and getting bitterly rejected by the wealthy Meowth named Meowzi that Meowth taught himself to speak and began to fully embrace his villain arc.

When Lauren Faust accepted the job of developing and showrunning a reboot of a beloved 1980s Hasbro brand, ultimately creating the story that became “My Little Pony: Friendship is Magic,” she brought her own childhood memories as a massive “MLP” fan to the table. But rather than simply rehashing the same syrupy-sweet characters that showed up onscreen in the brand’s early cartoons from the mid-’80s animated movies and 1992 series, Faust drew on her own style of play as a child to present a much more complicated world full of wonderfully complex characters. And you’d be hard-pressed to find one among them with a darker backstory than Princess Luna (Tabitha St. Germain), the younger sister of Equestria ruler Princess Celestia (Nicole Oliver) — especially since Luna led herself down a path so dark she literally transformed into Nightmare Moon and ended up banished from her homeland.

Princess Luna’s story is a tale as old as time, that of a jealous royal sibling who just can’t stand to be in the shadow of the big star. While Princess Celestia shone each day, Luna never quite got the same credit from the sleepy Equestria ponies at bedtime. Not content to live the quiet life of Equestria’s moon-setter, Luna embraced her rage, transforming with pure darkness and despair; a decision that would harm many ponies, leaving everyone — including Luna — struggling with lasting trauma long after she returned to her true self.