Safety Deposit Box

Maybe it's a stasis box too -- no time passes on the inside when the lid is closed.

So from her point of view she's taking him out to play with now and again when she feels like it, with days, weeks, or months going by in which she doesn't even think of him... but from his point of view what happens is: she opens the box and takes him out, does things to him, puts him back in the box, and then does it again the very next instant. This is his entire existence...