...Oh, and you know what? I just realized that they DID feature a cover of "All Together Now" on Sesame Street during its first season! Learn something new everyday...
Some more ideas:
* "This Diamond Ring" (The Anything Muppets)
* "Happy Together" (sung to a large letter U)
* (concept same as above, but it's this one song called "You Were On My Mind" or something like that. It was from the 60s, and I remember seeing it on some infomercial for the "60s Gold" CD collection")