Before it was made famous by The Muppets Show and the Benny Hill Show, the song Mah-Na-Mah-Na started it’s illustrious career in a 1968 Italian Mondo exploitation movie. Mondos are fake or pseudo documentaries about titillating subjects. This one is supposedly about the sexual mores of the Swedish. Svezia, inferno e paradiso or Hell and Heaven in Sweden has a lot of sexual content but also drugs and other depravities.
The tune, written by Piero Umiliani, is played as a bunch of Swedish girls in furs enter a steamy sauna. Its original title was Viva la Sauna Svedese (“Hooray for the Swedish Sauna“):

In 1969, the tune became a single under a new title: Mah-Na-Mah-Na

The first Muppets Show performance was by Jim Henson, Frank Oz and Loretta Long on the fourteenth episode of the show in 1969.

Piero Umiliani (1926 – 2001) was an Italian composer specialized in Italian Exploitation Cinema.

By photo of out-of-print 1970 LP sleeve taken by me, Fair use,en.wikipedia.org/w/index.php?curid=33179188