Last night I thought I noticed him limping (favoring is front right paw) a bit. It was pretty obvious that he was. lordaerith felt gently to see if anything was wrong/cut and when he got to Boris's shoulder, the poor cat hissed at bit. And when I just went to feed them, while he had eaten all of his food, he hadn't licked the bowl clean. If you know Boris, you know this is a big deal.
Nothing looks cut or imbedded in him, so he probably just strained or pulled his shoulder while running around or chasing his sister or something. If it doesn't look like he's getting better by Sunday night, I'll email the vet.