Reminds me of a time a few years ago when I was giving a talk on working memory capacity in children and decided at the last minute to throw in a cartoon on one of the powerpoint slides. I'm on the travel laptop in the hotelroom and it's 1:00 AM so I'm not looking at the cartoon that closely and my screen is only 12 inches so I can't really see the details of this cartoon I found on google of a girl in pigtails writing on a chalkboard.
So, I'm giving my talk, and up comes the cartoon on the giant projector screen, and I notice she's writing 100 times "I will not suck dick in class". That was not so good.