To me, few things are worse than when people sing the wrong words to songs. My sister Jaime used to do it all the time. It came to a point where I believe she was doing it deliberately to make me freak out. Well, she has a successor.
Nothing is worse than a five year old who gets a song in her head.
"La cockroach-atcha, La cockroach-atcha, la la la la la la ala..."
Dear Lord. And we were in the car and stuck in traffic.