In Mouse Trap, 2-4 players race around a track collecting wedges of cheese from 3 traps (constructed during setup but very much rendered in the Heath-Robinson/Rube Goldberg style of the the original).
Whenever cheese is collected from a trap, or at certain other times, the toilet in the center is flushed. This releases a ball, which will trigger one of the three traps at random. Trapped mice lose a wedge of cheese. The first player to gather 8 wedges (a full circle) is the winner.