A gruff-voiced Muppet “male” sings something that sounds like, “Munumina,” and some “female” backup singers reply in falsetto, “Doo doo didoodoo.” Repeat several times. Then the “male” goes off on an extended jazz riff on that theme, wandering off into the background, before he realizes the girls are waiting patiently for him. He hurries back and repeats, “Munumina,” to which they respond as they had earlier. No actual word is ever sung. It’s a bit of musical fluff.
I’m not sure this novelty song originated with the Muppets, but I think they popularized it, either in the late Sixties or early Seventies. You’d know it if you heard it, I’ll bet. Forgive my poor phonetic transcription of it, and thanks for your help.