The games consists of a toy barrel in either blue, yellow, red, or green. The barrel contains 12 monkeys, their colour usually corresponding to the barrel's colour. The instructions on the bottom of the barrel state "Dump monkeys onto table.

Pick up one monkey by an arm. Hook other arm through a second monkey's arm. Continue making a chain. Your turn is over when a monkey is dropped.

Barrel of Monkeys is a toy game first created by Lakeside Toys in 1965 which is now produced by the Milton Bradley Company. When Lakeside Toys originally developed the game using S-shaped hooks made from rubber and wire, they had intended to name it "Barrel of Fun," but found that both that name and "Barrel-O-Fun" were already being used by other game manufacturers.

Subsequently, the company decided to name their game after the related phrase "more fun than a barrel of monkeys" and remodeled the S-hooks into plastic monkeys. Original inventor was named Marx or Marks of Roselyn, New York.

Initially sold in a cardboard tube, Lakeside quickly produced a two-piece plastic barrel that completely replaced the cardboard version by 1968. Unlike the later mono-coloured Giant Barrel of Monkeys, this original version was composed of 12 plastic monkeys in three colours; 4 each in red, blue and yellow.

These Monkeys have also been used for modeling of polyhedral structures, including virus particles and other protein structures. In brief, a pair of monkeys can hook around each other in more than eighty different ways, forming quite stable links. The links may be either symmetrical or asymmetrical.

Repetition of an asymmetric link generates a helix. A symmetric link is self limiting, so that the structure cannot grow further unless a new link is used to join symmetric pairs. It is possible to generate structures with point, line, 2D or 3D symmetry by choosing two or three different links (from the 80 or more possibilities) and repeating them systematically. An enormous number of compatible combinations can be found by trial and error. Many are shown in the sources quoted above.

Any repeating unit can in principle be assembled in this way. The only unusual characteristic of the monkey is that its arms,legs, hands and feet are able to twist around each other to form many stable links. In this, they resemble protein molecules which can also link together in many ways.

The resulting assemblies simulate biologically important structures, but their symmetry follows general geometric principles. The monkeys provide a 'hands on' approach to understanding these principles.