Self-confidence +1. I remember in a silly general biology lab thing, 24 samples of fake bodily fluids were given to students, one or two of which were infected with the AIDS. This, of course, resulted in many sexual innuendos. Then at some point, the lab TA said the lights might need to go off to see the results of our fluorescent ELISA assays. I immediately thought "Shouldn't the lights have gone off while we swapped samples?" and then two seconds later, the funny guy in the lab said the exact same thing and everybody laughed and two other people even repeated the joke. I cried.