*sits up with a start -- her head had fallen forward on a large stack of books*
Ugh... Kate, I'm afraid there'll be a crick in your neck when we go back to normal. My first chance to sleep in six hundred years, and I spend it at a library desk! There's no justice in the world.
*wearily pulls another volume over, skims the index and table of contents... maaay or may not be nodding off again*
*some time later, sits up again sharply, then stands up; Kate's slender fingers tremble as they riffle through pages of notes -- and then Bob roars right above his open journal, unconcerned about the rest of the castle hearing him*
Castiel! Meet me in the Restricted Section, NOW!
[[If you're in Hogwarts, feel free to have happened upon Kate!Bob asleep at the desk. XD The rest of the action takes place in the evening, near (though they don't know it yet) the end of the body-switch event.]]