When I play with French people, for French people, or even while just jamming, we sometimes don't know the lyrics, or the singer doesn't speak english. So you'll often hear the singer mash some syllables together in an American accent, with the general "sound" of the lyrics. We call this "yaourt," or yogurt, which is exactly what's in that video.
It's a lot of fun.
Oh, and that's a great song.
