I remember a Pepsi ad I saw once and once only. It was after the little girl lip-synching the "Joy of Cola" song had been running a while. Apparently, they wanted to have a new ad, but they didn't have time to get the little girl in to shoot another commercial, so it was just the "Joy of Cola" jingle running with some general text graphics of the words of the song splashing here and there over the screen.

The problem was when they got to the chorus and were singing "Bah bah bah bah bah, the Joy of Cola," right on the screen, in big red letters were "Bah bah bah bah bah" -- the clear and immediate implication was: "Hey, drink Pepsi, you SHEEP!"

Like I said, I only saw it once. I'm amazed I saw it that many times...