Several of the early Neo Geo AES releases featured a socket on top of the home cartridge that allowed two home systems with the same cartridge to be linked together for up to 4-player action. For a long time there was a belief that no such cables were made, however a number were created in included beneath the trays of at least some link-up games (Riding Hero is the confirmed game, see picture). The three games were League Bowling, Riding Hero, and Thrash Rally. For an extended discussion about the Link-Up Feature, please see THIS thread.