Aye, we don't get it on regular television here anymore, either.
As for actors, yes it does, Larry David appeared in numerous episodes!...
... Not only as George's boss, but also as some crazy guy. On the television. Jerry has a dream... Something like that.
I actually think that Curb Your Enthusiasm is better than Seinfeld...............................
Larry David also handled the voice of Newman until Wayne Knight was cast to take over the role
I'm pretty sure Larry also barked like a dog off camera for the episode where Jerry ends up stuck babysitting a stranger's dog for the weekend