I had a co-worker propose the following riddle:  In a sealed room there’s a refrigerator with the door open.  Will the room increase or decrease in temperature?  I said it’d increase over time due to the 2nd Law of thermodynamics and after I got a blank-eyed stare stated that “the fridge generates more heat than it takes away”.  He looked at me grinning, said I was wrong, and stated that he never said it was plugged in.  I said his point was stupid and he called me unobservant, I shucked off the point until I remember as with most situations at work, there’s a XKCD comic that discusses it.  I found it.