What's the deal with Muppet crossovers?

Ok, the “Favorite Sesame Street bit” thread has got me thinking. You’ve got the Muppets (Kermit, Miss Piggy, Gonzo, etc.). You’ve got the Sesame Street Muppets (Oscar, Big Bird, Grover, etc.). To what degree is there crossover between the two casts? Did the Muppets make regular appearance on Sesame Street? Do Sesame Street Muppets make regular appearances in the Muppet movies? I remember in that old Sesame Street movie, “Follow that Bird”, Kermit the Frog was a TV reporter, but that’s all that comes to mind. Any thoughts?

Ahh, just realized I probably posted this in the wrong forum. If this belongs in MPSIMS or GQs, feel free to move it.

Kermit is the only Muppet Show muppet that was on Sesame Street, I believe. And the Sesame Street muppets have appeared as cameos in some of the muppet movies, most notably Big Bird in The Muppet Movie.

Then of course, some of the cast of Muppets Tonight was never seen on either of the other shows.

Last Sunday I watched A&E’s Biography Special on Sesame Street and they had early footage and there was a very early commercial “preview” of Sesame Street back in 1969 and the two Muppets that were talking about it were Rowlf and Kermit. I don’t know if Rowlf ever appeared on Sesame Street, but he was in a commercial for it. I believe that the Muppet Show was created because Henson realized the popularity of Sesame Street among adults, too. Muppet Show is just a very elaborate adult version of Sesame Street (at least with the Muppets, I mean).

Actually, Kermit and Rowlf are the oldest muppets. Henson was using them as characters in independent appearances on late-night talk shows and possibly (my memory’s fuzzy) his own afternoon puppet show back in the early-mid 60s. So it’s entirely possible that those two were the only muppets built yet, especially if this was before SS premiered.

Rowlf did make at least one appearance on SS. I have a vague childhood memory of him at a piano singing to some kid.

I seem to remember that show, but it was a puppy. (Real, not a muppet.) Very sweet.