And we don't know, Amadeus,

The story:

I believed for years that Nirvana was making a
poignant statement about themselves and classical
music. I was quite disappointed to learn this was
not the case.

I repeatedly forgot the proper line to the song and
inserted my own version of it. I still often sing
along to the song with my version of the line, much
to the bemusement of friends and family.