Basement Dweller / Western Animation

• In Adventure Time, one of Jake and Lady Rainicorn's sons, T.V., is revealed to be this in the episode "Jake Suit". Jake expresses his approval.
• Mookie from Atomic Puppet lives in his overbearing scooter-chair-bound mother's basement despite being the former sidekick of Captain Atomic and the rival of Atomic Puppet.
• Cluemasters from The Batman concocts his evil schemes from his mother's basement.
• Batman: The Brave and the Bold episode "Night Of The Huntress": The middle-aged "The Calculator" operates his evil ventures from his mother's basement. When Huntress comes to bust him, his mother is all too pleased that there is a girl here to see him.
• In the Bob's Burgers episode "Carpe Museum", school guidance counselor Phillip Frond reveals that he still lives with his mother. The museum director, whom he's been flirting with the entire episode, immediately loses interest in him when she learns this.
• Codename: Kids Next Door: "Operation: M.I.N.I.G.O.L.F." involves The Great Puttinski shrinking down Numbuh Two and challenging him in a mini-golf course complete with models of the world's monuments. The whole course is in his mother's basement. Numbuh Two still wins.
• Trent from Daria is in his early 20s and living in his parents' house with no job, and no formal education (he's not even entirely sure if he graduated high school), has no motive to go and find a job, and if he isn't sleeping, he's rehearsing with his band Mystik Spyral. Daria, who had a crush on him in the earlier seasons, once expressed that she at the very least hopes his music career pans out because she can't imagine him doing much else. He's definitely a far more sympathetic depiction of this trope, however.
• The Fairly OddParents! episode "Big Superhero Wish": The middle-aged writer of the Crimson Chin lives with his mother and receives a magazine called "Geeks Who Live With Their Mothers Monthly". Not that Denzel Crocker is any better...
• Fanboy and Chum Chum: Oz fits this trope to a T. He's an adult, action figure-collecting, obese comic book nerd who lives with his mother. They technically run a comic book shop together, although in "The Hard Sell", it's revealed they're unable to sell anything due to Oz's infatuation with the items.
• Futurama episode "Where No Fan Has Gone Before": Melllvar hits this trope dead center.
  Melllvar's Mother: Melllvar! Dinner time!
  Melllvar: Aw, but Mom, I'm playing with my collectibles!
  Melllvar's Mother: Now!
  [Melllvar groans and disappears.]
  Fry: All this time we thought he was a powerful super-being, yet he was just a child.
  Melllvar's Mother: He's not a child, he's 34!
• Wade from Kick Buttowski: Suburban Daredevil, while not a nerd but a severe slacker, tells Kick and Gunther that he lived in his stepmom's basement but she kicked him out... Turns out she lived in a trailer and the basement was just a hole in the ground underneath it.
• Kid Cosmic has Fantos the Amassor. While styling himself as a herald and loyal supporter of Erodius the Planet Killer, he comes off as more of a big Manchild and fanboy, whose "minion" is actually his mom who he still lives with.
• Frugal Lucre of Kim Possible operates his schemes of world conquest from his mother's basement where he lives. Taken two steps further, when the heroes gain access to his 'lair' not through their usual MO of breaking in through the roof or ventilation shafts, but by knocking on the front door and asking his mother if he was home. When Lucre and the heroes are gearing up to fight in the basement a few moments later, they're interrupted by his mother bringing a tray full of snacks and juice for her son and his "friends".
• In King of the Hill "The Witches of East Arlen", Bobby joins a group of "wizards" who appear to be basement dwellers as the leader Ward who looks middle-aged lives in his mother's house.
• In The Legend of Korra Book 3 (Change), one of the new potential Airbender recruits is a 22-year-old man who still lives with his mother. His mom, despite saying that he's "still trying to figure his life out" to try and justify it, is delighted by the idea of Tenzin taking him to the Northern Air Temple, just so she can finally get him out of the house. Three years later, not only does he join Tenzin and the other Airbenders, they also give him a job as a tour guide, and his parents are glad he has a job. However, he's embarrassed to see them at work.
• Legion of Super Heroes (2006) episode "Substitutes" has Porcupine Pete, who not only has his mom drive him and the other audition rejects around, but also has the best moment of his life ruined by his mother arriving and saying it's his nap time. Although technically Pete and the rest of the Subs are still teenagers so him living with his mom makes more sense, and this may count as a subversion.
• Coop from Megas XLR makes for a strange non-nerd (albeit very slacker) example. Upon learning that the Monster of the Week intends to destroy his house, he exclaims "My Mom's home! She'll kill me!"
• My Little Pony: Friendship Is Magic: Zephyr Breeze, the younger brother of Fluttershy, tries to reintegrate his parents' home at the beginning of "Flutter Brutter" because he can't find a job. His mom and dad aren't exactly pleased (since he's wholly insufferable), but they are too meek to straight-out refuse.
• The Slimer! segments of The Real Ghostbusters gave the gluttonous green ghost an archenemy in Professor Norman Dweeb, an eccentric scientist obsessed with capturing him who is shown several times to still be living with his mother.
• The Simpsons:
  • Comic Book Guy is subject to Geographic Flexibility. Apparently, someone thought this would make a worthy gag to have him living in his parents' basement after they'd already established that he lives above his shop (it's one of those business-on-the-first-floor-home-on-the-second-floor buildings common in small-town USA).
  • Most of the jokes about Seymour Skinner revolve around how he still lives with his beloved smother mother in middle age (although as with Frasier, he insists "she lives with me!"). Given Skinner has a paying job as principal of an elementary school (though he is revealed to only make $25,000 a year in "Skinner's Sense of Snow") while his mother Agnes is frequently shown as quite senile, he has a point.
• South Park: Jenkins the Griefer from the episode "Make Love, Not Warcraft". The main thing known about him is that he has played World of Warcraft so much that he's reached a level thought unreachable even by the designers — from which they conclude that he must have absolutely no life at all.
  "...But how do you kill that which has no life?"
• SpongeBob SquarePants: Bubble Bass is shown to be one, as first seen in the episode, "Moving Bubble Bass". When he gets fed up with his mother interrupting his fantasy talk show and making him do chores, he tricks SpongeBob and Patrick into helping him move his belongings to his grandmother's basement across the street.
• Star vs. the Forces of Evil: Dennis, Ludo's brother, is a grown man who still lives in his parents’ home, and they often complain that he’s not doing anything good with his life, blowing stuff up, and thus becoming a deadbeat like Ludo. Dennis eventually moves out of his parents' home.
• T.U.F.F. Puppy: The main character Dudley Puppy and the leader of D.O.O.M. Verminious Snaptrap are both shown to still live with their mothers. The former does eventually get his own place, but it's a treehouse in his mother's backyard, so there isn't much distinction.
• In Underfist, when Hoss Delgado was going to use explosive weaponry on the bad guys, his mother interrupts and tells the bad guys that Hoss is 48 and he still lives with his mommy.
  Mrs. Delgado: Hoss?
  Hoss: (in a high-pitched voice) Yes? Mommy?
  Mrs. Delgado: You're not pretending I'm dead again because you're 48 and you still live with your mommy, are you?
  Hoss: (angry and embarrassed) No mommy. (the bad guys laugh hard)
  Mrs. Delgado: Okay, you play nice now.
  Hoss: Yes mommy. (fires his cannon at the bad guys, creating a huge explosion)
• The Venture Bros.: Henchmen #21 briefly lives and operates his own comics supply business out of his mother's house, before being called back by The Monarch.
• A villain in WordGirl, Chuck the Evil Sandwich-Making Guy, lives in his mother's basement. (He tried to move into his own lair once, but got too homesick and moved back.)