Mah nà mah nà. I say it's a meme because The Muppets popularised it and did a callback to it at least once after its first appearance. It's lived in the consciousnesses of many people of a certain age and anyone else exposed ever since.

Very few people have actually seen the film it was written for. I know I haven't. It's a bit twisted that a song from what amounts to an adult movie ended up in a kids' show to be fair, but it happened. And the song is in my head.

Edit: If you are not yet infected, the following link is risky in that you'll end up with a new song in your head. Vid is SFW. It's from a kids' show after all. https://www.youtube.com/watch?v=TbZ_hTEOKZc

Edit II: Apparently the above first appearance might not have been on The Muppet Show itself, but on The Ed Sullivan Show where The Muppets appeared at least once.