Drop-In Character

"Strong Bad: Is there like a sign on my door that says, "Wanted: Everyone I Hate. Inquire Within"? King of Town: I didn't see one."

- Homestar Runner, "Strong Bad Email #142: secret identity"

A neighbour who drops in on a regular basis and mooches around. He or she is often a friend of one of the household kids who is either very annoying or very cute. Because he or she is the neighbours' kid and we never meet his or her parents, he can exhibit all sorts of zany behaviour without the need for too much explanation.

In most cases, the main characters have given up on trying to get the drop-in characters to knock, a la Kramer from Seinfeld, or Lenny and Squiggy on Laverne and Shirley. Considering how much of a pain in the ass this sort of drop-in tends to be, the viewer is sure to wonder whether the host has ever thought to just lock the door, but don't expect that to be addressed in the show. It's exceptionally rare to even see a lampshade hung here.

Sometimes the drop-in character's arrival is presaged by an ironic foreshadowing -- see Inadvertent Entrance Cue.

Compare Your Door Was Open.

For a different sort of "drop in character", see Face Heel Turn or Moral Event Horizon. For yet another different sort, see Suspiciously Similar Substitute.

Anime and Manga

 * Miu from Ichigo Mashimaro drops in by Nobue and Chika by jumping the roofs of their adjacent houses and climbing in through Nobue's bedroom window. She even does this in the middle of the night to sit on Chika's stomach, for no other reason than to be the Jerkass she always is. Heck, she even drops in through the window when the crew are staying at a hotel, purely out of force of habit.
 * Renge from Ouran High School Host Club has entrances that are more dramatic than most drop-in characters, sometimes rising out of the floor on a pillar.
 * Yotsuba&! is the extremely cute example of this trope. She doesn't distinguish much between her own house and her neighbor's house and even calls the next door neighbor mom "Mom" just like her own kids do.
 * And then there's Yanda, who drops in on the Koiwais to eat his lunch, much to Yotsuba's annoyance.
 * Vanessa in Madlax starts out this way.
 * Lucy from Fairy Tail is an inversion; she's the one that gets dropped in on... constantly... by everyone. People make themselves so comfortable at her house it's ridiculous.
 * Ikkyu, Nozomu's "one day friend" in Sayonara, Zetsubou-sensei sometimes plays this role, with the twist that he doesn't drop in at Nozomu's home, but rather at the school Nozomu nominally teaches at, which makes him a more bizarre example, as does the fact that he isn't really a close friend of the protagonist. Lampshaded once by Nozomu, who asks him "Why are you here? What is it you do at this school again?"

Comic Books

 * Jolyon Wagg from Tintin.

Live Action TV
"Ross: WE HAVE GOT TO START LOCKING THAT DOOR!"
 * Eddie Haskell on Leave It to Beaver may have been one of the first Drop In Characters.
 * In Friends, every character does this at one time or another, usually at least once an episode.
 * Slightly lampshaded at one point near the end of the series when Monica can't remember the last time her apartment door was locked.
 * Also lampshaded when Ross is about to finally tell Rachel he loves her, but is interrupted by ex-fiancee Barry bursting in the door and beating him to the punch.

"Monica: Hello, people who do not live here! I gave you a key for emergencies. Phoebe: We were out of Doritos."
 * And again in the last episode, where Monica and Chandler, about to leave their apartment for good, solemnly drop their keys in a dish for the landlord to pick up - followed by all the other leads adding their own key to the dish.
 * This is also mentioned by Monica, in episode 3.19, when she enters her house only to find Phoebe, Chandler and Ross there.

"Eric: Mom! Be careful. At any given time, there are at least 3 individuals in this house that would use that information to destroy me."
 * Howard on The Bob Newhart Show was a classic Drop In Character, often having just flown in or about to fly out.
 * Nick at Nite once ran a campaign including multiple clips of Howard asking "what's for dinner?"
 * On Newhart, this role was filled by Larry, Darryl, and Darryl.
 * Lenny and Squiggy on Laverne and Shirley.
 * On Happy Days the Fonz was originally a Drop In Character before ascending to Breakout Character status, while later on Fonz was himself dropped in on by Chachi.
 * Also on Happy Days: Potsie, Ralph Malph, Lori Beth, Arnold, Al Delvecchio, Jenny Picalo, Roger Phillips, Melvin Belvin, Pinky Tuscadero, Officer Kirk...pretty much every character on the show who wasn't a member of the Cunningham family wound up crossing their threshold uninvited at least once.
 * Spoofed in at least one of Cracked magazine's "Happy Daze" parody comics, as illustrated above.
 * As already mentioned, Kramer on Seinfeld is one of the most popular, well-known examples. A little more justified than other instances in that they lived in an apartment building with security so Jerry only had to worry about other tenants dropping in unannounced.
 * Technically George and Elaine are this too, they just don't fit the conventions of the trope nearly as well.
 * They eventually had to cut down on his drop-ins because the studio audience would applaud for like a year when he entered and throw off the timing of the scene.
 * In one episode, Jerry actually had the door locked for an unrelated reason leading to a loud crash as Kramer tried to perform his trademark slide.
 * Family Ties has several of these -- Skippy was the nerdy one, Nick was the punk one (well, TV-punk).
 * Kimmy, DJ's best friend on Full House. The opening credits actually have the Tanners practically closing the door in her face.
 * Until the character gets included in the regular cast, at least. Then the whole "closing the door in her face" thing gets dropped, replaced and subverted by the scene in which she opens the back door in her character introduction in one season.
 * Sure you're not thinking of Steve Urkel in the Family Matters opening? Because that was in there too.
 * I think the Family Matters one was the Winslows trying to push the door in to keep Urkel out. At no point in any Full House intro was Kimmy treated like that (for the 1991-92 season {the first after the Promotion to Opening Titles}, that one is the one where Kimmy cracks the door open)
 * "Bud", "Cockroach" and several of Vanessa's friends on The Cosby Show.
 * The Australian sitcom Hey Dad..! had several drop in characters over the years, most famously "Nudge". Inexplicably, one of the drop in characters, Ben, ended up moving into the family proper.
 * Steve Urkel of Family Matters is yet another example. The weird nerd kid from next door, who exhibits zany behavior, and subsequently takes over the show.
 * On Frasier, Niles was always just dropping by, though reasonably explanations were often given, usually involving Maris and her friends doing something that drove him out of his own house.
 * Six LeMeure on Blossom is a rare female Drop in Character.
 * Steve and Marcy, and later Jefferson and Marcy on Married... with Children.
 * Ed Norton, from The Honeymooners
 * In the British sitcom Birds of a Feather, the drop-in character, when faced with a locked door, smashed a window to get in while the main characters watched.
 * Willona on Good Times. This editor only recalls ever seeing Willona's apartment once, when she adopted a young Janet Jackson, but that's a whole other story...
 * The Sufficiently Advanced Alien Q was able to drop in on Star Trek characters, most notably Captain Picard, anywhere in the universe. Of course, Q was omnipotent, and any plot involving him would usually center on his actions, making him perhaps a better example of The Great Gazoo.
 * Inverted in Keeping Up Appearances, in which the main character, Hyacinth, forcibly drags Elizabeth, her neighbor, into Hyacinth's house and forces tea on her.
 * Usually in Royal Doulton teacups (...with the hand-painted periwinkles...). The fear of dropping these teacups has turned Elizabeth into an agoraphobic wreck.
 * Charley Dietz from Empty Nest would frequently drop into Harry's kitchen just to raid his fridge and hit on his daughters.
 * Lampshaded in the Coupling season 4 episode 'Nightlines' in which one of the characters barges into the home of another (due to her retaining the front door keys of anyone she's ever had a relationship with) which causes another to state that she has to stop doing that because 'this is not, repeat: not an American Sitcom'.
 * The Fresh Prince of Bel-Air has Jazz, who's both a "drop-in" and "throw-out" character.
 * Raymond's parents in Everybody Loves Raymond are constantly dropping into his home without notice.
 * Such unwanted behavior even makes it into the musical introduction.
 * Iola Boylan on Mama's Family. She never knocks, but her Catch Phrase (always said after she enters) is "knock, knock."
 * Maynard G. Krebs on The Many Loves of Dobie Gillis.
 * Pretty much the entire teenage cast of That 70s Show with regards to the Foremans' house, particularly the basement (though naturally they have no problem wandering about the rest of the house and enacting other elements of the trope, such as mooching food and pilfering Red's beer). Occasionally lampshaded, such as one time when Kitty mentions an embarrassing secret of Eric's aloud.

"Tia and Tamara: "Go home, Roger!""
 * Lampshaded again in one episode where Eric, Hyde, and Laurie are all grounded. Red goes around to perform a "bed check", with Eric having Donna in his room, Hyde having Jackie, and Laurie with Kelso. Then, Red goes down to the basement, where Jackie, Fez, and Kelso are sitting watching TV, like nothing is wrong.
 * Martin had a character simply referred to as "Brother Man", who occasionally invited himself into Martin's apartment through his window.
 * Reba featured possibly the worst example of this trope, as Reba's ex-husband and the woman he left her for felt perfectly justified in walking into her home without any form of notice or even knocking. This troper frequently wondered why the hell she never locked the doors.
 * Because said ex-husband and his wife have keys to Reba's place, it costs too much effort for Reba to change locks all the time just to keep them out, and plots advance faster without doors locked.
 * She did lock the door occasionally, but only for gags (though I believe one had Barbra Jean refusing to give up).
 * Clarissa's friend Sam on Clarissa Explains It All. He didn't even bother to use the door when he dropped in: he used a ladder to climb through Clarissa's bedroom window. As well, he had his own musical sting.
 * Not only that, but Clarissa didn't even need to look at him to know when he was coming up.
 * Well, the sound of the ladder being propped against her window was a fairly clear signal as to his identity.
 * IIRC, she'd often say "Hey, Sam" as a result of the musical sting before the ladder even showed up.
 * Likewise, Morgan in Chuck often uses the "Morgan Door" - Chuck's window.
 * Roger in Sister Sister.

"Jeff: We were debating how many times a year a man can drop in a study room in a dumb costume with irrelevant news."
 * On a somewhat related note, Mo from Smart Guy.
 * In Kenan and Kel, we never see Kel's home or family, while much of the action takes place at Kenan's home and his parents and sister are relatively major characters. Kel also hangs around Kenan's place of work, Rigby's.
 * In The Sarah Jane Adventures Maria's parents are divorced and she lives with her father, her Mum frequently drops in unannouced.
 * Bernard "Beans" Aranguren, in Even Stevens. He was essentially a parody of the Drop in Character, since the Stevens family couldn't keep him out of their house no matter what they did. And not only were his parents never seen, but the only episode where anyone tries to track Beans back to his house led two of the main characters to conclude that Beans was in fact an alien.
 * Sam and Freddie from iCarly, although they're part of the main Three Amigos, they were once called by Spencer "her two friends who never hang out at their own homes."
 * Being a recurring side character, Freddie's mom is a classic example of the trope.
 * At one point Spencer mentions he almost didn't recognize Sam and Freddy since they weren't sitting on his couch.
 * It should be noted that due to Sam's skills with a lockpick, locking the door on her is pretty much useless.
 * Monroe Ficus was this in Too Close for Comfort, generally when he appeared, it was obvious that he was going to say or do something that would irritate Henry Rush. Eventually when the show became a first-run syndicated series, he would become a live-in character, when he moved into a third floor addition of the Rush house, after his apartment is torn down. By the time the series was rechristened as The Ted Knight Show for its final season, he reverted back to being a drop-in character when the Rushes moved from San Francisco to nearby Marin County.
 * Tsk, tsk, who forgot Rose from Two and A Half Men?
 * Maxine Shaw from Living Single.
 * Kenny from The War at Home. We do see his parents, though.
 * He even lives with the Golds for a while, after his parents have kicked him out for being gay.
 * That's My Bush brilliantly spoofs the drop-in character by having him drop into the White House.
 * Penny from The Big Bang Theory. Howard and Raj could count as well.
 * Landlord D. Álvara in Brazilian sitcom Toma Lá, Dá Cá. And at a certain point, she appeared everytime someone spoke her name. (to the point that the characters became Genre Savvy and tried to stop utterances of it)
 * Aunt Jackie from Roseanne neatly solved the question of why she's not locked out by being the title character's sister.
 * Dean Pelton often does this to the study group on Community. Lampshaded in one episode:


 * Pretty much the entire cast of Sanford and Son other than the title characters were this with Esther, Grady and Bubba being the most frequent offenders.
 * Buffy the Vampire Slayer. Spike once he became allied with the Scoobies in Seasons 4 and 5.
 * Barney Stinson in How I Met Your Mother. Lampshaded in an early episode when Ted mentions that sometimes they couldn't even figure out why they were friends with Barney. The same episode concludes that they tolerate his antics because he tended to get them into interesting adventures.
 * Ed on Northern Exposure. He has a habit of already being in the room before someone even notices he's there, and he's been asked on multiple occasions whether he believes in knocking.

Newspaper Comics

 * Elmo, the neighborhood kid who often drops in on Blondie's Dagwood, usually while he's trying to nap. On at least one occasion this was lampshaded by Dagwood saying, "I've got to put a lock on that front door."
 * An inversion of this, of course, would be Dennis the Menace (US), whose title character frquently dropped in unannounced (and unwelcomed) on crotchety neighbor Mr. Wilson.
 * Sally Forth has one of these in Faye, the best friend of the Forths' daughter Hillary. She often pops up at odd times, and the strip will lampshade this by having Sally or Ted sarcastically ask whether she's moved in with them.

Radio

 * On Fibber McGee and Molly, almost every supporting character fit this trope. In practically every episode, a succession of them would drop in at 79 Wistful Vista to chew the fat with the Mc Gees.

Video Games

 * Half the cast of the Touhou series make a habit of dropping in at the main character's residence unannounced and mooching around. The worst offender is probably Yukari, the Teleport In Character.
 * In the games, the player character serves this function, especially in the fighting games. Drops in, fights, leaves. After beating up everyone, they FINALLY find the real culprit!
 * A Sim with 10 Outgoing points in The Sims 2 will do this if your controllable sims make friends with him. You can still lock your door, though.

Web Original

 * Before she became an Ensemble Darkhorse and started appearing in nearly every video, Nella was this to The Nostalgia Chick. (Now back to being this as the real life Nella moved further away.)
 * '90s Kid just appears out of nowhere in Atop the Fourth Wall ' s reviews (and rarely other people actually talk back to him).
 * Warning! Readers' Advisory has a handful: mad scientist supervillain Herr Doktor Innis du par Nachteltaffen, Friendly Neighborhood Vampire Nachzehrer, Lethal Chef Red Chef, and a surprisingly affable Cthulhu.

Western Animation

 * Inverted on Aqua Teen Hunger Force, where the main characters are the ones who are always dropping in at the weird next-door neighbor Carl's house -- usually to use his swimming pool without permission. In one episode, he builds a laser grid around his house to keep them out. Naturally, the results are less than optimal...
 * Ron Stoppable is pretty much this, almost never seen at his own house, he's even there when the Romantic False Lead is hanging out with Kim Possible during The Movie. On the occasions when he is seen at his own house, it usually foreshadows an event of real significance, such as an impending move to Norway or the acquisition of an adopted sister (none of which his parents ever tell him about in advance).
 * Foster's Home for Imaginary Friends has Goo and Cheese, with an episode for each centered on keeping them out of the titular Home. Of course, it doesn't work.