Rational and real – math humor
Someone on Ravelry.com had this avatar, I had to share it here because it was so funny.

This got me thinking. It might actually be a fun assignment for students to look up cartoons or joke on Math-related humor. A few students share these in the classroom once a week for extra credit, and they have to explain the humor to folks in the class. Or the teacher can find the cartoons, share it with the students as part of a Journal entry prompt. Students have to explain in their own words why the cartoon is funny and the background knowledge behind the joke.
I found a few that made me chuckle:

