found this on the net:

9 Fun Things to Do During a Boring Lecture

1) When the professor asks a question, raise your hand. If the professor calls on you, point to someone in the inayofuata row and say "He knows." Pick a different person each time.

2) Buy a watermelon. Give it to the professor. If he/she asks, say "They were out of apples."

3) Bring a fishing rod. Try to catch things on the professor's desk.

4) Bring a tape player and a tape of a thunderstorm. Keep it hidden. Sometime during the lecture, start the tape, stand up, claim that the professor has angered the gods and leave. Watch to see how...