After the performance of the "three shell game" on casino nights - I tell the spectators that the reason I don't lose is that the peas have a mind of their own - they have "pea brains". I then place two more peas on the table to match the chips we've been playing with during the game.
Start with three chips and three matching coloured peas (Green, White and Red). The order doesn't matter.
As you move the chips - cover the pea with the shells.
Let the spectators tell you where to place the coloured chips.