A man walks into a bar and orders a beer. As he's enjoying his drink, he notices a jar filled with money sitting on the counter. Curious, he asks the bartender what the jar is for.
The bartender explains, "We have a challenge here at the bar. If you can make our resident grumpy old man, Bob, laugh, you get all the money in the jar. But be warned, no one has ever been able to do it."
Intrigued, the man decides to give it a try. He walks over to Bob and whispers something in his ear. Bob suddenly bursts out laughing, tears streaming down his face. The man collects the money from the jar and the whole bar erupts in applause.
Amazed, the bartender asks the man, "What did you say to Bob that finally made him laugh after all these years?"
The man grins and says, "I just told him that I bet him $100 that I could make him laugh."
The bartender laughs and shakes his head, impressed by the man's cleverness. And from that day on, Bob was never known as the grumpy old man at the bar again.