So, here's a thing. Apparently, back in 1957, a young Jim Henson did a series of television commercials for Wilkins Coffee. In addition to providing an important life lesson about NEVER DOUBTING THE WILKINS, these commercials provide a glimpse at a sort of proto-Kermit.
There's more interesting information about Henson's early career at Network Awesome, including a bunch of other early commercials. Most are just as strangely violent as these, and you'll find ur-forms of other familiar muppets. I came across this via Boing Boing.