A common con game in fiction, particularly in comedy. It works like this: Someone challenges a person to a "friendly game" of something, be it cards, some kind of sport or something else. At first, they seem to be bad at the game and will repeatedly lose to the other person. Then they will suggest a wager. The minute the wager is made, they suddenly become good at the game and beat the other person hands down. A longer, and more expensive version, is to lose a series of small bets and then apparently attempt to bluff the mark into going away with a very large, dangerous bet that completely overwrites the previous losses.