“The question is, what is a Mahna Mahna?”
“The question is, who cares?”

The Mahna Mahna song (Piero Umiliani, 1968).

Performed by Mahna Mahna and the Snowths, (The Ed Sullivan Show, 1969). From Google Video.

See also:

song history on Wikipedia,
lyrics on poppyfields.net,
audio (mp3) on latke.net,
video (mpeg) on mahnahmahna.net.