Closet Sublet

A character who, for one reason or another, is living in another character's wardrobe/closet. For some reason the "tenant" is usually female. Happens a lot in anime, apparently because in Japan some people do indeed spend time in their closets during certain types of weather. That's half the reason why even smaller houses over there have such big closets. Of course, apartments and capsules in Japan don't have closets at all.

In addition, following from Trope Codifier Urusei Yatsura, it's a way to allow the Magical Girlfriend to live with the hero without the two having to share a room.

Examples of Closet Sublet include:

Anime and Manga

Read or Die the TV series has Maggie sleep in a closet. She likes small spaces.
Lum in Urusei Yatsura is the Trope Codifier.
Although the floorplan for Misato's apartment shifts constantly from episode to episode, Neon Genesis Evangelion seems to have Asuka force this arrangement on Shinji.
- There are floor plans of it in some of the supplementary books. Basically, Shinji got dumped into the study/sewing room.
This is basically the entire plot of Rizelmine, where the main character's Unwanted Spouse takes up residence in his walk-in closet.
While Rukia of Bleach is in the mortal world, she stays hidden inside Ichigo's closet, to his chagrin. She eventually gets an upgrade by sharing his sisters' bedroom. She prefers the closet.
- The fancomic Coming Out of the Closet had Rukia (as a revenge scheme for Ichigo complaining about this trope) rent out the closet to other members of the cast. To quote Ichigo: "That title gives out the wrong idea!"
  - Something similar happens in some of the Omake shorts in the anime, although it's not clear whether Rukia is actually renting the space, or has simply told everyone back home that providing closet lodgings and temporary storage is one of the duties of a Substitute Shinigami like Ichigo.
Kiri Komori will randomly show up in Itoshiki-sensei's closet (or any other dark, enclosed space) when the "plot" requires.
It's hinted that Maika in Magikano frequently hides in her brother Haruo's closet and watches him sleep, as part of her utter obsession with him and her ultimate goal of some serious Brother-Sister Incest.
NieA in NieA 7.
Ren-Ren-Ren-Nagusaran-Rensia-Roroonren-Nakora in DearS. Since it's divided by a shelf halfway up its length, several other characters take up the bottom space (with Ren holding the upper space) over the course of the series.
Doraemon sleeps in Nobita's closet.
Tenchi Muyo!: Ryoko is occasionally like this, only she tends to prefer rafters to closets.
- Washuu winds up taking residence in an extra-dimensional space created using the Masaki broom closet under the stairs.
Konoe goes into Akuto's closet at least once to "observe" him in Demon King Daimao.

Film

In the Val Kilmer movie Real Genius, Lazlo lives in Mitch and Chris' closet. Sorta. The closet actually contains a lift to his hidden laboratory in the steam tunnels below the school.
In Charlie Kaufman's movie Synecdoche New York the main character Caden Cotard moves into his ex wife Adele's closet after taking the place of her maid, presumably without Adele's knowledge, living out the rest of his days there.

Literature

Harry Potter lived in the closet under the staircase under the Dursley's home prior to the major events in Book One.
In a non-romantic, male example, Spider from Anansi Boys takes up residence in the tiny walk-in closet belonging to his brother, "Fat Charlie" Nancy. Or rather, his immense penthouse with a scenic view of a waterfall in the Amazon jungle takes up residence there. And Spider absolutely refuses to leave. Hilarity Ensues. So does a number of other things that are mostly entertaining when they don't happen to you.
In the book The Sugar Queen, there's a girl living in another girl's closet.
In The Westing Game, Turtle insists that her bedroom was designed to be only a closet. Her mother disagrees, but someone else who comes looking for the two of them asks why they're in a closet.
In the Mercy Thompson series, Stefan once crashed for the day in Mercy's closet. Justified, as he's a vampire and it was the only space in her trailer that could be entirely sealed off from light.

Live Action TV

The 2005 American sitcom Committed had a 'dying clown' living in the female lead's closet. When asked about this little eccentricity by a potential suitor, she reveals that she is subletting her apartment and a condition of the lease is that the clown gets to live in the closet until he dies. "They're used to small spaces, you know the cars."
One recurring sketch on Nickelodeon's Turkey Television was an E.T. parody starring Adam Reed as a boy with a friendly alien living in his closet.

Web Original

In Dan and Mab's Furry Adventures, Mab takes up residence in Dan's closet after her Faery Grove gets blown up. Granted, its more a case of using his closet-door as an entrance into her own, private pocket-dimension, but it evokes much the same effect when she pops into and out of her "home".

Western Animation

Another male example is Fry from Futurama, who lives in Bender's closet. This is actually an inversion of the usual space issue in that Bender's "closet" is actually the size of a regular room, while the space where Bender stays is the size of what we ~~Americans~~ Meatbags would consider a closet. When Fry first proposes living there, Bender comments that it's odd, but they stick with that arrangement.
- Keep in mind, this is all after Bender wants to stay in Fry's closet when Fry gets a really great apartment. Futurama was about as much irony as possible in it's early days.
For several seasons of Family Guy, an apparently evil monkey lived in Chris's closet.

Real Life

Truth in Television: there was a recent case in Japan where a homeless woman secretly lived in a man's closet. The man noticed only when he realised that the amount of food he bought and ate didn't match up, and set cameras around the house.
George Clooney admits he used to live out of friends' closets when he was broke and couldn't afford rent while struggling to break into show business.