After a semester of a senior math seminar with one student always bringing up "but you assumed the axiom of choice!" (mostly non-seriously), the gradstudent tea

After a semester of a senior math seminar with one student always bringing up "but you assumed the axiom of choice!" (mostly non-seriously), the gradstudent teaching it decided for his, and last, presentation to show this theorem. It was pretty wild as I had never heard of it before (being a physics-math person). Very cool. (The seminar was on knot theory but I had more fun with Banach-Tarski).