Two fishermen are out on the lake when one of them drops his wallet overboard. Before the man can grab it, a carp comes along and bats the wallet into the air. Before it hits the surface, another carp a few feet away leaps out of the water and bats the wallet in the air to a third carp. The carps continue to bat the wallet between the three of them, making a game of it.
So the second fisherman turns to the first and says, “Hey, look! Carp-to-carp wallet!”