I finally found the time to watch the sketch using my off-air copy. Most of the Muppets who appear are Whatnots, though the Dog has appeared in a few sketches. I think he's the Dog that Dyan Cannon chooses in her closing number. However, some specific Muppets do appear - Zelda Rose (she's the one who's told to "watch her feet"), Nigel, Lou (Lousie Gold's gypsy character) and a member of Bobby Benson's Baby Band - Lou is playing his mother in the sketch.
Another Muppet who appears is the yellow-haired "hippy" character who sometimes plays in the jug band. He's in the "Why Can't We Be Friends" number; his line is "Why don't we drop our guns and all shake hands?"
Hope that helps.