It twitches a little when touches, mostly by reflex, early evidence of developing nerves even if Steven doesn't have total control over it yet. It's weird, though, so Steven can't help but shiver a little, reaching back to put his hand on Greg's as if trying to feel what's going on, exactly. When he does, it will make the increasingly defined claws replacing his fingernails all the more obvious.

"Yeah... What is it?" he asks, sounding a little bit concerned but mostly just confused. He has a thing on his butt? That is probably ominous, right? He'd just like to know more specifically what it is, because growths just showing up places reminds him of his early attempts at shapeshifting.

At least Greg's comment makes it clear that there's no cat face growing out of his bum.