Kermit tries to sing the standard song "What Kind of Fool Am I?" from the musical Stop the World - I Want to Get Off,
in an appearance on The Ed Sullivan Show on May 31, 1970. He accompanied himself on piano, but was repeatedly interrupted by Grover.
It has been found but in black and white quality. A color version still exists but is unavailable.
https://www.youtube.com/watch?v=lHqceaAirc8 The black and white version.