'SCUSE ME WHILE I FLUB THIS SONG: From time to time, I hear what I will call anomalies in pop songs. Flubbed lyrics, seemingly incorrect notes being played on instruments, and odd noises in the background. This site offers a nice overview of many such anomalies, as does this one. Fans of the Beatles will want to check out this mind-numbingly complete list of errors in songs of the Beatles.
My favorite? During the instrumental break of the song "Wendy" by the Beach Boys, at the 1:19 mark, there is an unmistakable cough in the background. Let's just say that I listened to that song many, many times as a lad.
I'd normally provide links to many of these songs, but it's often very hard to hear many of the errors unless you are listening to a CD either with headphones or with high quality speakers.