As you probably know, the world of Muppets didn't begin with the Muppet Show. Many people will place Sesame Street as the origin of the Muppets. Sure, Kermit got his start as a reporter on Sesame Street, but there was a Muppet way before that. I may not be old enough to have seen it, but in the early '60s Rowlf the Dog was the first Muppet to become a star. He was cast member on The Jimmy Dean Show way before he played Dr. Bob in Veterinarian's Hospital on the Muppet Show.
Here is one of his few cards that pays tribute to his first gig:
TBCB Muppets - #7 Rowlf the Dog
I really couldn't resist dipping my toes into the Sesame Street pool as well:
TBCB Muppets - #8 Oscar The Grouch
I had forgotten about his best pal, Slimy, until I delved deeper into Muppet Wiki:
TBCB Muppets - #9 Slimy
I feel kind of bad for entombing Slimy, but not too bad... 'cause THAT is hilarious.