Manchild/Western Animation


 * Adventure Time:
 * The Earl of Lemongrab is an interesting version of this. Physically he's eighteen at the youngest, but because he was born in a laboratory, he's only about one year old chronologically. He acts like a bratty little kid trapped inside the body of an adult, mainly because he IS a very young brat who happens to be an adult, too.
 * He and his brother/clone/boyfriend have kids together... and they're STILL immature manchildren.
 * Jake also very much resembles this at times, to the point where one wonders if he's an English Bulldog, as he closely resembles physically, or if he's a Golden Retriever. His son Kim Kil Wan even says that Jake acts like a child.
 * Ice King also acts like this as he throws tantrums and treats being grounded literally. Unfortunately due to the magic of the Ice Crown which made his way. Pretty much "sadness and madness" accompany anyone who uses magic,and it's notable that wizards are technically their own race.
 * Cinnamon Bun is shown to be "basically 30" yet he owns a night light and cries a lot like a child while looking up to Kid Hero Finn. Turns out this is because he wasn't finished developing, as in he was literally undercooked. Going to help Flame Princess by moving to the Flame Kingdom allows him to grow by literally being able to finish baking. He becomes much more competent and mature (also a lot bigger, going from Finn's height to about twice that .) He's still kind-hearted and he still looked up to Finn to emulate him as he grew (he named his giant fire wolf steed Jake II for starts.)
 * The animated version of Beetlejuice. The majority of the inhabitants of the Neitherworld are fairly mature. Beetlejuice most likely expired in his late 30s, but he's mentally about eight, and a childish prankster who hangs around with a twelve-year-old Lydia in an Intergenerational Friendship.
 * CatDog: Despite being an adult, Dog acts like a kid, for example he likes reading comic books, playing in the park, throws tantrums, and is rather naïve and innocent. Cat even describes him as being "like a little puppy".
 * Mr. Delmas of Code Lyoko has shades of this—plays games on his computer, for instance.
 * Gravity Falls:
 * Soos is described as this by the show's promotional material and website. Given that he's a semi-Cloud Cuckoolander who's One of the Kids, this is a given. Even said so by Grunkle Stan in the season 1 finale, saying "you're a good man...child, Soos".
 * Deputy Durland and Sheriff Blubs also qualify as they both love reading spooky ghost stories and making friendship bracelets and went candy hunting on Halloween. They also giggle like children a lot. Durland is shown to be a bigger one than Blubs.
 * OK K.O.! Let's Be Heroes: A minor character on the show is Pird, a neurotic Butt-Monkey bird-man who escaped from a scientist's lab but, since he's technically only a few years old, he struggles to live in the outside world and is always pestering others (mostly Enid) for help learning basic things like how to wash his hands.
 * The Mayor from The Powerpuff Girls eventually wound up becoming this.
 * Regular Show:
 * Pops save the fact that he's the opposite of Literal-Minded.
 * Rigby is this too. He may be 23, but he acts like an out of control teenager most of the time.
 * Mordecai, to a lesser extent. He's a lot more level-headed and less impulsive than Rigby, but just as eager to slack off and do childish things.
 * Steven Universe:
 * Amethyst. Some of her antics are reminiscent of a teenager acting out. Her yelling "I don't wanna!" when Garnet tells her to go back to the temple in "Tiger Millionaire" is a good demonstration. She's actually quite young in comparison to the other Gems, having been created on Earth instead of hailing from the Gem Homeworld. This is further enforced by the fact that during Greg's flashback in "Story for Steven" she's much younger in appearance than she is now.
 * Greg was definitely this in his earlier years, refusing to work to support himself and mooching off other people for food. He's matured somewhat, but still prefers living in a van to a house and keeping a relatively unkempt appearance.
 * "Jungle Moon" reveals Pink Diamond to have been this, trying to get attention from Yellow Diamond in the same manner a child would do with his or her elder and throwing a tantrum if she doesn't get what she wants. She eventually grows out of it.
 * White Diamond accuses Steven of acting like a child while throwing an epic tantrum over Steven not being Pink Diamond.

White Diamond: You're just a-a-acting like a CHILD!

Steven: I am a child. What's your excuse?
 * The Ridonculous Race:
 * Surfer dudes Geoff and Brody are 19 years old yet they both act like children.
 * Owen becomes this in the show as he is also 19 yet he carried a teddy bear around with him until he accidentally ate it.
 * Rock and Spud, who form the Rockers team are said to be in their late teens yet they are implied to be rehearsing music in the garages of their families and Spud in particular is shown to be very lazy and motivated by junk food such as Choco oinks.
 * Time Squad: Buck Tudrussell is shown to be a man somewhere in his 30's yet he frequently acts much like the age of his 8 year old time traveling partner, Otto, as Tudrussell sometimes throws tantrums, sleeps with a teddy bear, and sucks his thumb. His other time traveling partner, Larry 3000 even calls Tudrussell a man child in " Ex Marks The Spot".
 * Total Drama: Brick also has shades of this as he is a military cadet who refuses to leave anyone behind but he Screams Like a Little Girl, wets his pants, and sleeps with a night light on.
 * Uncle Grandpa takes this to extremes. He's shown be a very bizarre man who lives in his large R.V. and takes children on adventures to solve their problems.
 * Xiaolin Showdown:
 * Jack Spicer is a young man who is apparently in his early 20's there have been many signs of him acting very childishly. These hints include girly screaming, constant whining, and he was revealed to often sleep with a night light on. He also plays with the shen gong wu as if they were toys. This is mostly due to the fact that his rich parents did not raise him as much as they should as they often send him money in a vain attempt to make up for this.
 * Kimiko's Dad is a child on the inside as she told her friends. When we meet him, he's a exciteable man who is also a very famous video game developer (which may explain a bit.) Despite this, he knows when to foot his foot down (like when he discovers his new associate is actually Pandabubba, a mobster. He is zombified as a result.)