John Cleese indefinately. Especially the PIgs in Space segment.
"This be not an intercom! It Be a PAYPHONE!" You can tell he wrote some of the material he was in. It has a very John Cleese feel to the writing.
I dont really take much thought in the guest stars. Maybe its cause I dont know who half of them are. But I would have to say Alice Cooper and Elton John.
Funny story about Alice Cooper. Only until recently I had NEVER heard an alice cooper song sung BY Alice Himself. My dad thought that was pretty sad so he got me an alice cooper cd. Now I love Alice Cooper The Alice Cooper episode was THE one episode I HAD to see.
And Elton John, well, I just like his voice (except when he hits those really high notes)