A professor was too ill to teach his course, but didn’t want his students to go without. He audio taped his lecture, and sent it in to be played during his class. The experiment went so well, that the professor started taping his lectures and sending them in even after he felt better.
After several weeks of this, he decided actually to attend the class himself, and give his lecture live. When he arrived he found an empty classroom, with 120 tape recorders all set to record his talk.