I like the answers that have come in on this one. I think it could be valuable, though I don't know how to reword it. Just wanting to collect what made you laugh isn't a good enough criteria.
The third answer is less on-topic to my mind, perhaps because it is only a language issue, where the others are misunderstandings about math. Ahh, that's it! Being able to understand why students misunderstand is important for us (teachers). Thinking about it through humor can help us.
New title proposal: When student misunderstanding about learning math becomes humorous
But you all can do better than that.
Do you see the value in this?