In the early 90's Nintendo had a contest in different school campuses throughout the US. The person to beat Super Mario Bros, Rad Racer , and World Track meet under a certain time won some cool prizes and got a copy of World Championships cartridge. This cartridge contained all three games and some switches on the top left to change the time settings to complete the games. It is unknown how many cartridges are out there, but as of this day these cartridges can sell for tens of thousands of dollars on an online auction.A special edition gold cartridge was also released, but is way more rare than the standard gray one. If you want to make a fortune selling one of these, go out to a local flea market and search for these hidden treasures!