Why not sow confusion by making it only do this 5% of the time, so random people are SURE it happened to them and everyone else thinks they are insane.
I've posted this before, but anyway, the brilliant Monty Python released a record that sounded different when you played it sometimes!
Quote: "[This record] is particularly notable in that it was mastered with two concentric grooves on side two, so that different material would be played depending on where the stylus was put down on the record's surface. For this reason it is sometimes referred to as a "three-sided" record
The album did not have a track listing, so that this feature would come as a complete surprise to listeners, who might on a second listening hear material they had never heard before, creating genuine confusion.
Since the record had two concentric grooves, they were spaced considerably apart, halving the length of the playing time. Subsequent editions of the vinyl incorporated both grooves sequentially as separate tracks, eliminating the double groove." Unquote.
Source:
http://en.wikipedia.org/wiki/The_Monty_Python_Matching_Tie_and_Handkerchief