People post these everywhere all the time, but I saw this one and loved it. My favorite part is that the teacher circled the elephant with a question mark:

Peter, you drew an elephant instead of an arrow here. I can't understand why you'd do that, I went over it at least three times in class.

And then underlined "elephant," as if she'd just found the error in his formula.

Well, there's your problem, Peter. You wrote "elephant" instead of "6.97x." Also, you didn't show your work. No points for you, I'm afraid.