"Three-Person Chess" is a chess variant game designed by Sheldon and featured in "The Wildebeest Implementation". The game uses a non-standard, three-sided board with transitional quadrilateral-to-triangular tessellation to solve the balanced center combat-area problem, additional (or fairy) pieces, and different rules for capture, move order, and game objective, etc.
Known pieces invented by Sheldon are:
- Serpent and Old Woman: The first pieces invented. When the serpent slithers to an opposing player's piece, that piece is considered poisoned and will die after two more moves. Unless, it gets to the old woman in time, in which case she sucks out the poison, turning her into the "Grand Empress", a piece combining the power of the knight, queen, and serpent it also gains the royal crown.
- Prince Joey: The King's feeble-minded but well-meaning cousin. Every time he moves, there's a one-in-five chance he'll kill himself. Though it is unknown if this piece was implemente, and it is unknown how you would know if he killed himself.
- Catapult: Can fling pieces. Unknown whether it can fling all pieces (but it can definitely fling a bishop) or anything else about it.
- Gorilla: Nothing is known about this piece, but the space "Queen's Gorilla Two" is mentioned.
- Transporter Pad: Moves pieces from one space to another. The new location of the piece is decided by spinning a wheel with place locations on it. It is unknown whether it can transport all pieces (but it can definitely move a rook) or anything else about it.
- Golf cart: This can (assumedly) be equipped to any piece (in the show Leonard asks when the pawn can use it). It can be used when it is finished charging or when the player lands on the time machine.
- Time machine: When a piece lands on the time machine, the golf cart can be used without waiting for it to charge. It is unknown if the time machine can move or whether it can be used for anything else.
- The Beekeeper: Nothing about this piece is known, apart from the fact that it can release a swarm (which can cause checkmate), move, and capture a pope.
- The Pope: Nothing about this piece is known, apart from the fact that it can be captured by the Beekeeper. It is assumedly the most important piece in three-person chess and the player loses when this piece is checkmated, similar to the king in regular chess.
- Jet Pack: This piece can be equipped to the Pope, and presumably any other piece. It is unknown what it does, but judging by the name it might allow pieces to hover above the board or fly to different spaces. In the case of the Pope, it appears to be a surefire way to avoid capture by the Beekeeper.
Sheldon originally plays an unfinished version with imaginary replicas of himself. The final revised game is played by Sheldon, Leonard, and Howard, while Raj waits to play the two victors. In this match, Sheldon employs a catapult to fling his bishop to Howard's Queen's Gorilla two. Howard then moves his rook to a transporter pad and comes out at Leonard's Queen's Bishop five-and-a-third, placing Leonard in check. After Leonard inquires when a pawn is allowed to use the golf cart (to which Sheldon informs him when it's done charging or you land on the time machine, duh), Leonard moves his Beekeeper to King 12, capturing Sheldon's Pope and releasing a swarm for a checkmate on Sheldon. Disappointed, Sheldon wishes he had given his Pope a jet pack.
- "Three-Player Chess" really does exist, but Sheldon's version is much more exaggerated.
- "The Serpent" as chess piece: in Sir Terry Pratchett's Discworld fantasy series, there is Assassins' Chess, where an extra piece, the Assassin, moves in a remarkably similar way with remarkably similar intent and may stab or poison the "client", or chesspiece on the receiving end. The Assassin chess board also has unspecified extra squares and files called "slurks" (how they are organised is not clear) allowing for the Assassin pieces to move invisibly and pop up in unexpected places.