Gyromite

Gyromite (also known as Robot Gyro) is ... designed for use with the Robotic Operating Buddy. Gyromite is one of two games in Nintendo's Robot Series, the other being Stack-Up. The opening screen of the game shows the title Robot Gyro, the Japanese name of the game for the Family Computer. Essentially, the Gyromite game program is unchanged from the Famicom Robot Gyro cartridge, and in fact many Gyromite cartridges contain the circuit board from a copy of "Robot Gyro," attached to an adaptor that allows the game to be played on NES systems. Famicom games had 60-pin connectors, so the adaptor converted the game so it can be used with the 72-pin connector in an NES. Internationally minded collectors may look inside Gyromite cartridges for a Famicom cartridge adaptor, though these pin converters are rare, and many Gyromite carts were made without them.

Source: Wikipedia, "Gyromite," available under the CC-BY-SA License.