One of the music teachers in my school had a class of year sevens, and put a film on the screen via the projector (the projector was connected to both the DVD player and his laptop) and at the end of the lesson, instead of turning the projector off, he switched the projection to his laptop accidently and it turned out he was watching a porno. so it came up, massive on the screen, in front of a bunch of 11 year olds.
Not exacly on topic but i thought it was funny at the time. Of course he got kicked out.