I think the part of it she enjoys is the trouble and chaos it causes for people. Sometimes the swaps can put people in unfortunate situations, because they're not ready to deal with the problems that come with trading places.

[this leaves him wondering, if you swapped with a cat would you be amused by a feather on a string? maybe you would be. maybe it's instinct...]

Not to mention all of the napping in sunbeams that they do.