Tim DeKay, Peter's actor, has an extremely unique face to begin with. There's something unusual about the shape of his lips -- I've been trying to diagram what, because it doesn't precisely bug me but I'd really like to put it into the fic and can't quite figure out how.

I do like, though, that it's an unusual face -- there's a real diversity of appearance (not necessarily racial, just visual) in the cast, and it's something I value in other shows as well. I like it when the people aren't supernaturally pretty or identical; I love that we get such a variety of looks on the show.