Well, ya gotta start somewhere.
Airing in 1974, this special (intended as a pilot for The Muppet Show) doesn't yet quite have all the familiar elements in place. Kermit is a minor character, and the host is some bland guy with sunglasses whose name I can't even remember.
The guest star is Mia Farrow, and she appears in one cutesy musical number or sketch after another. It's not her fault; apparently Jim Henson and co. leaned heavily on the "cute" on this show. The second pilot, "Sex and Violence," would go straight for the comedy, and is much stronger as a result.
The one interesting concept to come out of this whole show is the idea of the Muppets all living in a house together. This idea wouldn't be used again until 25 years later (!), in 1999's "Muppets from Space."
At this time, this pilot is not available on video or DVD at this time, so you'll either have to get it in a tape trade or hope the rerun shows up on cable somewhere.
If you do get to see it, keep your eyes open for an Ernie and Bert cameo at the end.