The game consists of a transparent plastic tube, plastic rods called straws (normally numbering 26 to 30 in total and of various colours - yellow and red predominantly) and a number of marbles (usually around 32 in number). The base contains four separate numbered trays and the straws are passed through holes midway of the tube to form a lattice "web". The marbles are then placed in the top of the tube and held in place by the web.
At the start of play, the entire tube is rotated so that a hole in the base of the tube is aligned with the active player's tray. Players take turns removing a single straw from the tube while trying to minimize the number of marbles that fall through the web and into their tray. Once a player has committed themselves to a particular straw by touching it, they must remove it. The player who accumulates the fewest dropped marbles wins.
The onomatopoeic name of the game derives from the sound of the marbles tumbling to the base of the tube when a straw is removed.
The game is still available today, manufactured and marketed by the Milton Bradley Company in the UK and by Mattel in the USA, although the modern version uses a pink tube rather than the original purple-colored tube. There are also other versions of it, such as a Toy Story-inspired version that uses a tube shaped like a rocket ship and Little Green Men figures instead of marbles. In addition, the KerPlunk Game to Go features a collapsible tube, making it more portable than the standard version. Another game has also been released known as KerPlunk 2. The rules are the same, except the marbles that come with the game are colored and, after falling, move around a spiral pathway similar to that of a Gumball machine. It also has flashing lights and an assortment of sounds.