Hmm. I hadn't thought about that. I think I'm pretty quiet about taking the earplugs out (I don't get out of bed before I do it) but I guess I don't know for sure.
The cats have plenty of toys and, of course, the best toy of all -- each other to chase. I also just got them a new distraction this weekend: I put a cat door into the opening of the window between my apartment and my screened-in porch. Dogs, cats, birds, squirrels, deer, and insects to watch! Plants to eat! So far it's really only one of them who's taken advantage of it, though.
I don't take the earplugs out when I get up to use the bathroom but from the way they react when I wake up hungry and slip out to get a snack I'm pretty sure they know the difference between morning (when I'm supposed to be getting up) and the middle of the night (when it's strange and interesting that I'm up).