Monster Roommate

"Christine: [Recorded] Hi, you've reached the Tittles. We can't come to the phone right now. If you want to leave a message for Christine, press one. Bentley: For Bently, press two. Tarfal: Or to speak to or worship Master Tarfal, Underlord of Pain, press three."

- Angel, "Quickening"

Heroes tend to lead very... interesting lives, full of so many strange and fantastic sights and events that before long he's Seen It All, or at least dealt extensively with one type of non-mundane creature/phenomenon. As a result of this, or coincidentally, the character now casually lives alongside or in close proximity with an alien, ghost, vampire, mutant and/or robot (though not necessarily all in one character).

The nature of the arrangement varies. They might be allies of long standing, the monster came with the apartment as an unadvertised "bonus" and they've since hit it off, or both have made the completely mundane arrangement to share living space. It doesn't even have to be The Unmasked World, any monster that can fool Muggles is going to have to pay the rent, and it's sometimes convenient to share space and bills. If they're Vitriolic Best Buds, expect them to claim they keep the other as a "pet".

The setting doesn't have to be a Fantasy Kitchen Sink for this trope to happen, it just needs one difference that makes it Like Reality Unless Noted, and the character has to live right next to that thing. For maximum effect however, the character's house might become a full blown microcosm of the world's supernatural scene.

The "roomie" might be a Nice Guy ghost, a personable Fully-Embraced Fiend of a vampire, the hero's Yamato Nadeshiko Magical Girlfriend, or one of the Mad Scientist's Mascot Mooks that has been reprogrammed/retrained. If Tom develops an Unwanted Harem, each girl will be from a different monster race. Mind the Fur Against Fang.

Expect a lot of Cross Cultural Kerfluffles and humor. Two Gamers on a Couch frequently uses the Monster Roommate as a pet or one of the gamers.

Compare Pals with Jesus, where the hero is friends with a powerful cosmic or mythical figure, and Pet Monstrosity, where a monster is kept as a pet.

Anime & Manga

 * Doraemon - the titular robot cat lives in Nobita's closet (one of the earlier examples).
 * Urusei Yatsura - Ataru has an oni living in his closet (possibly a pun on the Japanese slang for Pretty Freeloader).
 * Similarly, in Bleach, shinigami Rukia lives in Ichigo's closet (much to his displeasure)
 * In Mahou Sensei Negima, Kotaro starts staying with Natsumi and Chizuru after a little incident that resulted in amnesia. He gets his memory back, and he's been staying with them ever since (even using Natsumi's surname so he can pass as her "little brother". Considering they're well on the way to Official Couple, one has to wonder what that implies.)
 * The plot of Magical Girl Lyrical Nanoha A's begins when the four Human Alien  Wolkenritter appear before Hayate and start living with her.
 * Brigadoon Marin and Melan - Melan, a flying alien cyborg with weapons for hands, moves in with Marin and her human family in order to protect her from other aliens that try to kill her. He is treated as a member of the family by everyone in the house.
 * In Death Note, Ryuk, a Shinigami, lives in Light's room, and describes himself as being his roommate.

Film

 * At the end of Beetlejuice, the human Deetz family is living with the ghostly Maitlands.
 * The Ghost and Mrs. Muir (1947)
 * My Favorite Martian (1999)

Literature

 * The short shory "Living With the Harpy" by Tim Pratt is about, well, just guess.

Live Action TV

 * The Ghost and Mrs. Muir (1968-1970)
 * My Favorite Martian (TV) (1963-1966)
 * The Addams Family (1964-1966) lived with The Thing, as well as frequent visitor Cousin Itt, and YMMV on the monstrousness of some of the others living in the house (eg. Lurch).
 * The Munsters (1964-1966) inverted the trope (perhaps before it was fully developed) with family of token monsters and a human live-in relative Marilyn.
 * On Buffy the Vampire Slayer, there was the period where Spike lived in Xander's basement.
 * On Angel, Cordelia shares her apartment with "Phantom Dennis", the ghost of a previous tenant whose mother walled him up to prevent him from running off with his girlfriend. (Except we only rarely "saw" Dennis past the episode establishing him.)
 * He was referenced or spoken to/of in anytime an episode featured Cordelia's apartment. He was even shown helping Cordy cover up the escalating damage her visions had been doing.
 * Lorne also filled this role quite a bit in later seasons. See also the page quote. Both Buffy and Angel were regular employers of this trope.
 * SARAH, the Smart House on Eureka, might qualify. Some people are certainly freaked by the idea of living inside HER and her actions/over-reactions in one of the later first season episodes made her the Monster of the Week when she thought Sheriff Carter was going to leave town.
 * The show Being Human (UK), where a vampire and werewolf move into an apartment that they later realize is haunted by a ghost. They all get along better than you might expect.

Video Games

 * Reimu of the Touhou series has many youkai she's defeated visiting her shrine on occasion for a Spot of Tea. One of them, the little oni Suika, even lives with her.
 * The Soldier of Team Fortress 2 is roommates with a magician. They don't exactly get along well.

Webcomics

 * David and Nancy in Ow, My Sanity.
 * In a side-comic of Too Much Information, Maddie shares her room with what is, essentially, the larval form of a 'cosmic horror' type entity. He seems to exist mostly for the benefit of Fish Out of Water jokes.
 * A variation in Eight Bit Theater, where it's heavily implied that Fighter and Black Mage have been traveling and living together for a very long time (they met up after the both got kicked out of their respective schools (Black Mage for giving an entirely new meaning to the word Evil, and Fighter for having the attention span of a rock) and they've been together ever since). It may have contributed to Black Mage's frequent bouts of omnicidal mania. Exhibit A.
 * Tedd of El Goonish Shive lives with Grace his part-human, part-alien, part-squirrel shapeshifting girlfriend.
 * In Wapsi Square, Tepoztecal, the Aztec god of alcohol, has spent much of the comic living at Monica's place.

Western Animation
"Arthur: Are you aware your roommate is a hideous monster from another dimension with evil plans for world domination? Thrakkorzog's roommate: Listen, a good roommate relationship is based on a respect for privacy."
 * Lilo and Nani from all the Lilo and Stitch movies and the television series.
 * In Ugly Americans, Mark lives with Randall, a zombie. Of course, this is a series where the monsters considerably outnumber the humans, so Mark doesn't see anything particularly strange about his living arrangements, even though Randall has brain cravings that seem reminiscent of a recovering alcoholic.
 * The Tick (animation) once faced against an evil alien named Thrakkorzog, ruler of dimensio... Errr... Apartment 14-B. He was roommates with a man who was barely even aware that he was sharing rent with a Blob Monster from outer space.


 * Tick himself can also be considered an example, a Nigh Invulnerable Cloudcuckoolander superhero rooming with a mild-mannered former accountant (who wears a moth costume, but that's neither here nor there).
 * Futurama: Human Fry lives with Bender, who, for those not familiar with the show, is a robot.
 * Specifically, Fry lives in Bender's apartment. Fry is Bender's Monster Roommate.
 * More than that. He lives in Bender's closet. (Which is as large as a 1 1/2 apartment), while the apartment itself is as large as, well, a closet.
 * Aqua Teen Hunger Force's Master Shake moves in temporarily with the legendary Dirtfoot.