Sesame Street - "The Original Mah-Na, Mah-Na" (1969)
https://www.youtube.com/watch?v=x3YkkmMxjV0
Here's the original Muppet performance (in best quality) of "Mah-Na, Mah-Na" (or "Mah Nà Mah Nà", composed by Piero Umiliani, the song first written for use in the Italian film "Sweden - Heaven and Hell").
This performance first aired on Episode #14 of Sesame Street, which premiered on Thursday, November 27th 1969. (three days later, on Sunday, November 30th 1969, a modified version of the sketch appeared on The Ed Sullivan Show)