In medical school there was a professor who pimped us regularly as a teaching tool, but without any sense of sarcasm, cruelty, or abuse. He was actually very tongue in cheek about it. He would occasionally throw out a "gold star" question, which promised to be a more difficult or esoteric question and if you answered it correctly you were rewarded with a brief moment of glory, and if you could answer three gold star questions in a row you got to go home and take the rest of the day off. Needless to say, if you ever got two gold star questions correct, the third one was going to be a real doozy. Thus, no one ever got to take the rest of the day off. But it was all in good fun.