In my high school history class, the teacher was talking as always and suddenly we hear this loud crash come from the back of the classroom. We all turned around to see what had happened and this girl had been reaching too far over to another desk and actually tipped her entire desk over, with her in it, and we quickly burst out in laughter.
In college psych, we were talking about what we find attractive in members of the opposite sex, and the professor called on some volunteers to describe. Well, this class had about 150 people in it, and this one girl described her boyfriend in the army and how she loves the uniform and the cap they have to wear. Just then, a guy comes into class late and walks almost to the front of the room. The closer he gets to the front, the more the laughter builds as people see him and finally, we all just burst out in laughter because he was in ROTC wearing the army uniform and was wearing the cap she liked. The poor kid had totally no clue why we were all laughing- musta thought he had something on his pants, but after he sat down, we told him what happened- and I noticed he was all red.
In my history class, we each had to get in front of the class and give a presentation about a specific book of our choice. Well, I'm totally awful at speaking in front of people. Something about 50 eyes all looking at me creeps me out. So, I'm up in front of the classroom and my speech is totally not going the way I had rehearsed it in my room, and I start to panic. In one line that I was giving, I was supossed to say "The men could divorce their wives...". As usual, I botched it by saying "The men could divorce their women..." The whole class erupted in laughter.