I don't recall the exact client or ad campaign...I think it was Suzuki... but in the 80s I worked at an ad agency and we slipped the fbomb into the mice type at the bottom of the page. It was a prank intended for the legal team upstairs who's job it was too proofread. But somehow it slipped past them and got out the door. Oops. We were all expecting to get fired over that one. Thankfully, no one ever caught it. Learned my lesson. Now I only do that on headlines.