hammerspace
Hammerspace is a fictional, extradimensional expanse used to explain the sudden appearance or disappearance of an object or any signs of that object's existence. It is most often used in the context of a character seemingly pulling an object out of thin air or from a space smaller than the object itself, but in other contexts, it may be used when a character hides or conceals certain body parts (e.g. breasts, penis) in clothing that they are larger than.
E.g. A carpet is laid flat on the floor. Upon removal of the carpet, a large box is found underneath it, despite there being no prior evidence to the box's presence, such as a large box-shaped lump in the carpet. Such an instance would invoke the use of this tag.