A legend, mostly untrue, but with a true occurence or known origin. Please note that as the alt.folklore.college FAQ diverges from the alt.folklore.urban FAQ, different FAQs may reach different conclusions. T. No such luck with Fermat's Last Theorem. F. Princeton students rioted in celebration of the solution to Fermat's Last Theorem. T. Stanford math grad student murders advisor with ball-peen hammer.
All universities have policy of when it's officially okay to leave class when professor is late.
Others possibly have one, too. T. Most European universities couldn't care less when you came or left. Prof. lectures class on sugar content of ejaculate. Science class students take swab from inside of cheek and examine under microscope. One group sees odd organisms and calls prof. who looks and declares that it's sperm.