Jim Henson, right before Sesame launched, had begun producing a series of specials featuring some of his Muppet characters interacting with humans. Hey, Cinderella! was the first of these, produced in Canada in 1969, and landing on ABC a year later, after Sesame took off.
In 1971, the networks stupidly passed on Henson's next project, an adaptation of The Frog Prince, which ended up airing in syndication in May of that year. I seem to recall that the folks behind My-T-Fine & Royal puddings were the sponsors, but don't hold me to that.
Anyway, Kermit (Henson) serves as narrator and is also part of the cast in this production, which also would mark the American debut of Canadian actor Gordon Thomson, who'd later turn up in the 80's on Dynasty.
The following video was taken from when the special aired several years back on Disney Channel.
Henson would do one more syndicated special, adapting The Town Musicians of Bremen into The Muppet Musicians of Bremen, but then, The Muppet Show came along around 1976, and you know the rest.