It's a fair bet that you've heard "Mahna Mahna" from The Muppet Show. If you're of a certain age, just mentioning "Mahna Mahna" starts the tune in your head, and you're off to the races! (Doo-doo-dee-doo-doo, doo-doo-dee-doo!!) But while most of us think of the song as the opening number on the original Muppet Show, its first Muppet rendition came on an early episode of Sesame Street, performed by a trio of then-nameless "anything Muppets" just messing around. Check this out, and note how the backing vocals go "bah-dee-pee-tee-pee" rather than "doo-doo-doo":

The song got more play on The Ed Sullivan Show later in 1969, now with the characteristic Snowth singers. By now, the male singer is a character named Bip Bippadotta and has flaming orange hair:

Versions then appeared on The Dick Cavett Show, This is Tom Jones, and Pure Goldie before its most famous turn on The Muppet Show in 1977 as the first sketch ever aired on the show. This is the version I know best, and it defines The Muppet Show for me:

But let's rewind once more -- the original song was written by Piero Umiliani for an Italian film about...wait for it...sex in Sweden! What?! The film Svezia, Inferno e Paradiso (translated: Sweden, Heaven and Hell) first used the song in 1968, making that its first appearance ever (albeit with no Muppets). In those days, it went by "Mah Nà Mah Nà" and served as the score to this scene involving a sauna (don't worry, everyone remains clothed):

And that, my friends, is the original, original "Mahna Mahna." In 2011, the Muppets released it as a single and it's been stuck in my head ever since.