The game's prototype was invented in 1964 by University of Illinois industrial-design student John Spinello, who sold his rights to renowned toy designer Marvin Glass for $500 and the promise of a job upon graduation, which was not fulfilled.
It consists of an "operating table", lithographed with a comic likeness of a patient (nicknamed "Cavity Sam") with a large red lightbulb for his nose.
The general gameplay requires players to remove these plastic objects with a pair of tweezers without touching the edge of the cavity opening.
In the American and Australian versions, players take turns drawing the top Doctor card from the deck, offering a cash payment for removing a particular object.
The player in control uses a pair of tweezers (dubbed "Electro Probe" in earlier versions), connected to the board by a wire, to remove the piece without touching the metal edges of the cavity in which it rests.
In 2002, a brain surgery version was released, requiring the player to pull pieces out of a wisecracking Cavity Sam's head, within 15 seconds.
A Doctor Who version of the game was released in Great Britain, where players get to "operate" on a Dalek in order to (from the product description) "make it strong enough to take over the world.
Family members take turns pulling pieces out of an oversized Operation gameboard, and then running through an obstacle course to eventually place them in a container at the end of the course.
If a player fails to pull a piece without touching the side, or drops it while going through the obstacle course, they must move to the back of the line, and it's the next person's turn.
Each piece is worth a specific amount of points, and whichever team has earned the highest score when time expires wins.