The song came from a sauna scene from the 1968 film Sweden: Heaven and Hell, and while the movie does show a lot of Scandinavian skin, it's not porn. It's a mondo. For those who don't spend their free time watching poorly produced films of antiquity, a mondo is an exploitation film subgenre where the movie is presented as a documentary or pseudo-documentary about controversial subject matter like sex or drugs or violence. The educational aspect of the film is really not important and the "documentary" angle is just an excuse to showcase sex or drugs or violence and get asses in the theatre seats, or in the 1980s, to get people to buy videos. The Faces of Death Collection is perhaps the most famous example of mondo films. I didn't watch those to be educated. I watched them for the gore.
Sweden: Heaven and Hell is supposed to highlight the seedy underbelly of 1960s Sweden by showcasing contraception and teen pregnancy, biker gangs, wife swapping, lesbians, etc., but really it's just an excuse to show busty Swedish blondes frolicking in the snow. And there's nothing wrong with that.
Anyway, back to the Muppets. It is true that Jim Henson "borrowed" the Mahna Mahna song from a raunchy Swedish movie, but the movie is an exploitation film and not porn.... Bork! Bork! Bork!
Here's the song in Sweden: Heaven and Hell.
And here's the Muppet version.
If you want to see some puppet boobies, look here...
Or here...
