Back when I was in junior high school, I had a science teacher who would often show documentary films to us, and in those olden days, it was through the use of a projector with film rolls. Often after showing them, he would tell us that he would let us watch some of it backwards, if we promised "not to unlearn it". It was kind of utter chaos and we would be laughing about things like people eating - but in the backwards form of it, they would be pulling the food out of their mouths, driving backwards, aircraft landing backwards, a whole slew of pretty funny things. I think he was the one teacher who really knew how to make science interesting.