There's a math teacher at Biola University near L.A. named Matthew Weathers. And he always goes viral around April Fools' Day, because he messes with his students by creating an elaborate video for his overhead projector.
This year, he pretended to accidentally draw on the screen with a marker. And he set it up so it looked like he was talking to a clone of himself on the screen, to figure out how to get the marker off.