I learn a lot about my students when I'm grading their work.
One student, in particular, is very quiet in class. Very low key. Despite this, I know he has a great sense of humor. How? Well, he frequently will leave comments off to the side of his quizzes. Also, he's a bit of a comic sketch artist. Everything he works on will have at least one doodle on it. Even better, his doodles are often related to whatever we are learning about.
For example, Otto von Bismarck, Wilhelm I, & the Ems Telegram:
Of all of his doodles so far, though, this one is my favorite:
It's always nice to have a good laugh when you are in the middle of grading a large stack of midterm exams.