Didi Conn, Barry Pearl and Michael Tucci haven't changed. At all. I'd still recognise them on the street, which is more than I can say for the rest of the supporting cast.
Kelly Ward looks... indefinably freaky. I don't know what it is - something about his eyes, maybe. Or - possibly - too much surgery in the last 25 years. Shame, I always thought he was cute in the movie.
Jeff Conaway still has a nice smile and lovely eyes, but he's no longer quite as gorgeous as he was back then. Interesting fact that came out - seems the man was quite a slut on the set. Slept with most of the female cast and crew, sometimes more than one at a time, according to the other T-Birds.
Jamie Donnelly looks spookily like a woman who works at my uni. I think it's just the pure-white hair, that's not such a common thing when you're as young as she is.
Dinah Manoff is probably the most attractive of them all, now. She looks like someone's sexy mum, with emphasis on the "sexy". Actually, she looked wonderful, nowhere near as old as the rest of them, though they must all be around the same age.
I don't think I need to comment on John Travolta and Olivia Newton-John, do I? ;)