I shave my legs.

The story:

I had **sumed I was wrong upon hearing them the first time. This was revealed to me when I read about them in the CD booklet upon buying the disc. A few years later, I hadn't listened to the song in a while and decided to turn it on. I started to sing along, and, upon reaching the part, my brain chose to sing the wrong lyric.

When I realized what I had done, I began laughing so hard I fell out of my computer chair and caused myself a couple of jammed fingers. I still cannot listen to the song with a straight face to this day.