Mahna, Mahna, Doo, doo, do, do, dooo.
It's a song sung by, amazingly enough, Mahna Mahna, a hippy male puppet with a deep voice (done by Jim Henson rather like Rowlf the dog and Dr Teeth's voices mixed together) and scarey eyes the blink without any eye-balls in the sockets. He sings the, "Mahna, Mahna," parts and the "mar, na, ma, mer, mahnu mah muu," parts. (Kind'a hard to write down, by the way) And then two pink creatres who looks basically like um, like, er, like well, like...pink tubes, I guess. Standing upright with arms that don't have armrods, and they have large eyes too, and eyelashes, and pink horns. They sing, "Doo, doo, do, do, dooo" in responce to his, "Mahna, mahna."
It goes roughly:
Mahna, mahna (doo, doo, do, do, doo) x 2
Mahna, mahna (do, do, do. Do, do, do. Do, do, do, do, do, dooo, dooo, do, doo)
Then Mahna, Mahna does a little scat thing. "Mah, neu, muh, menmahnema muh, etc"
Then it repeats itself three or four times.