Surprised in the sense of not even knowing they were in it before you watched it, I mean.
I still remember being a pup and watching The Muppets Take Manhattan
for the first ever time. And aside from the live-action Muppet Babies interlude (which I thought was *very* cool, having more or less grown up with the Muppet Babies
cartoon rather than the real Muppets, only later did I realise this was done *first* of course!
), the other thing I was gobsmacked by was seeing a pre-TNG Cheryl 'Gates' McFadden in the movie. It just blew my world apart seeing Dr Crusher interacting with the Muppets.