Lock ‘n roll: a tale of three cartridges

Game Genies—there were versions available for the NES, the Super NES, and the Game Boy, as well as the Sega Genesis and the Game Gear—worked by intercepting communications between the console and game cartridge. In order to circumvent the CIC chip, Super 3D Noah’s Ark required that you first plug an ordinary licensed Super NES game into the top of its cartridge and then plug Super 3D Noah’s Ark into the console. This combination is considered the “real” version of the game, and its unusual release strategy is the famous result of tight time constraints—Sega released the first half of the game as soon as it was ready, and released the second half as this lock-on cartridge later in the year10.

Source: writing.markchristian.org