Hammerspace is a convenient place for characters to carry around mallets, anvils, fridges, or whatever else they need to advance the plot in a very small space. But what do you use to store a whole person?

This trope occurs when whole characters manage to hide themselves away into incredibly small spaces. It could be inside a shoe, or a suitcase, a jewelry box, in a friend's pocket, or behind a telephone pole.

Where ever the hideaway is, it must be an area so small that even if the character were to scrunch up and get squeezed into the space, it would still be too small for them, making Hammerspace the only plausible explanation for how they could possibly fit.

When characters use Hammerspace to disappear behind narrow poles, they are Behind A Stick. If a character turns out to be living inside a Hammerspace Hideaway, then it is probably a Clown Car Base instead. If we can see inside the Hammerspace Hideaway, then it will likely be Bigger on the Inside. Compare Party in My Pocket. See Behind the Black for similar situations resulting from the Rule of Perception.

Examples:

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Anime and Manga

In Mahou Sensei Negima!, Kaede's Artefact is a cloak (essentially a flat piece of tattered cloth) that can hide several people inside... it does have a fully furnished house in there after all.
In One Piece, Capone Bege has the ability to miniaturize things to fit within his body (the inside of which appears to be like a castle).

Comic Books

Scott Pilgrim can fit inside Ramona's shoulder purse.

Literature

There is that addition to the good ship Gay in the Robert A. Heinlein novel The Number of the Beast.
The Real Mad-Eye Moody in Harry Potter and the Goblet of Fire.
Chiron's Super Wheel Chair in Percy Jackson and the Olympians, where he hides his horse legs.
Not the most extreme example, but in the first book of The Mysterious Benedict Society trilogy, Reynie, Kate, Sticky, and Constance are forced to squeeze into a very small crate to hide from Mr. Curtain. The illustration does not at all look comfy.

Live Action Television

Wizards of Waverly Place: Alex invoked this to sneak Harper onto the S.S. Tipton by hiding her away in her suitcase. Justified in that the suitcase is magic.
There was once an episode of Scrubs where Turk sneaked JD around in his backpack.
One common gag in Shake It Up involves cute kid Flynn stowing away in his sister CeCe's suitcase, even when it's filled to capacity.
- In the Good Luck Charlie crossover episode, Flynn, along with Rocky, Ce Ce, and Deuce, all stowed away in Teddy's luggage. Rocky and Ce Ce hid in her suitcase, Flynn hid in her carry-on, and Deuce hid in her purse. Yeah, her purse.
Danger 5 reveals Stalin's moustache is one of these. Seen here.

Tabletop Games

Several types of Exalted have access to Charms that allow them to store objects Elsewhere. Lunars, however, can actually learn Charms that allow them to create tiny little dens in Elsewhere, safe places they can escape to on a moment's notice.

Video Games

In The Legend of Zelda: Majora's Mask, the Deku princess somehow gets put into one of Link's bottles, despite being normally almost as tall as Link himself.

Western Animation

SpongeBob SquarePants: One episode had Patrick's head come out of a hat box, which was itself in a television box.
Animaniacs: Dot had a special box in which she keeps a gigantic monster. The Warner brothers themselves can pop out of incredibly small places as well.
Ed, Edd n Eddy: The Eds often end up in some very small places.
- Eddy once managed to stuff himself into a bucket.
- Edd managed to fit inside his sock hat.
Looney Tunes: Bugs Bunny is known for stuffing some of his foes into rather tight spaces. For example, in "Bugs and Thugs", Bugs stuffed two fully grown gangsters into a rather small oven...twice!
- Another gag is the folding box. put someone in it, fold it like cardboard, then fold it again... and again...
Fairly OddParents: "I will now hide inside my own pants. Presto!" Timmy succeeds... until Vicky yanks him out.
"Peter, get out of the fridge!"
The closet doors from Monsters, Inc..
Danny Phantom uses this plenty. One wonders how a soup can can hold an unlimited amount of ghosts. It's even lampshaded at one point:
Danny: How on earth did they cram all of you into the Spectre Speeder?
Ember: You ever been stuck inside your stupid Thermos? Compared to that, it was the Taj Mahal in there!

Real Life

One variation on a very old joke about a scientist, a mathematician, and an engineer ends with the mathematician inside a can of beans.
Several people smuggled girlfriends/wives out of East Berlin in some impossibly tight spaces like a suitcase (or two) and a car seat (the person was literally inside the hollowed-out car seat).

Added Alliterative Appeal