Here are my ideas:
I've Got Two Legs: Sung by a veddy British chap who also dances.
Everything is Beautiful: Sung by three Whatnots resembling Vincent Price, Peter Lorre, and Boris Karloff, with Boppity, Gloat, and Uncle Deadly on backup, along with Svengali (Peter Ustinov ep.) on pipe organ and one of the punk band members from the Debbie Harry episode on tambourine. It could be set in a creepy castle on a stormy night.
Up, Up, and Away: Sung by the Electric Mayhem in a hot air balloon. I know Rowlf played this on his piano in the Madeline Kahn episode, but they've done most songs more than once on TMS, so what the hey!
Imagine: Sung by a Whatnot ballad rock-style group called Jerry Marvin and the Wild Bunch. Jerry Marvin would be a Harry Nilsson Muppet, so to speak. (LOL)
Silver and Gold (from Rudolph the Red-Nosed Reindeer): Sung by Rowlf.
Forty-Seven Gingerheaded Sailors: Sung by Kermit, Fozzie, and two male Whatnots in sailor suits. I'm not sure if that's the title of the song, but I heard it sung in a bunch of Jeeves & Wooster episodes.
Let It Be: Sung by "The Paul Seerf Quartet", four Whatnots made up to look like Bela Lugosi, Ed Wynn (Uncle Albert in Mary Poppins), W.C. Fields, and Sidney Greenstreet ("the fat man" in The Maltese Falcon"). The whole concept came from the album "Paul Frees and the Poster People". Should you not know who the late, great Paul Frees was, you know Boris Badenov, Ludwig von Drake, and the original voice of the Pillsbury Doughboy. "Seerf" is, of course, "Frees" spelled backwards.
Hanging On the Telephone: Sung by a Debbie Harry Whatnot and three male Whatnots in punk clothes, all of whom are stuffed in a telephone booth (think "Telephone Rock"). Soon, we could see several Muppets waiting on line and complaining about it.
BlueAM