We all know it, and once you’ve read this, you probably won’t be able to get it out of your head for the rest of the day (sorry).

But did you know that the iconic — yes, slightly irritating — Muppets theme song didn’t actually originate with Jim Henson’s puppet-filled TV show?

“Mah Nà Mah Nà,” as it is called, was written by Piero Umilani and made its first appearance in the 1968 film “Svezia, inferno e paradiso” (“Sweden: Heaven and Hell”).

The film is a “softcore mondo,” a Swedish term for “exploitation documentary,” a movie genre in which softcore pornography is dressed up as a documentary to give it a faint air of respectability.

The song soundtracks a scene some 50 minutes into the film, which “shows contraceptives for teen girls, lesbian nightclubs, wife swapping, porno movies, biker gangs, and Walpurgis Night celebrations. It also examines Sweden’s purported drug, drinking and suicide problems.”

And yet, there might even be a use of the song even more offensive to Muppets fans than its appearance in a dodgy Swedish skin flick.

In 1997, a sample of the song formed the basis of the debut single by British girl group Vanilla, titled “No Way No Way.”

Long rumored to be the result of a bet by rival record company heads about who could get the worst song into the charts, the song frequently appears on lists of the worst singles and worst music videos of all time. Check it out below — brace yourself:

Vanilla, what did the Muppets ever do to you?