The existence of id Software is largely due to the willingness of its founding members to create a PC port of Super Mario Bros. 3. Nintendo (needless to say) rejected the demo, and the developers used the same technology to shaping Commander Keen … the rest is history.
In 2015 John Romero shared on the web a video taken from the PC version of Super Mario Bros. 3, while today we discover that that demo was delivered in the hands of the curators of the Strong National Museum of Play in Rochester (New York State), where will be preserved forever as an important piece of gaming history.
Digital Games Curator Andrew Borman says he found the demo floppy disk among other items donated to the museum by an anonymous developer. After having tested its operation, verifying the validity of the material using DOSBox, Borman has kept the code both in physical and digital format. There are currently no plans to show it to the public, but things may change in the future. In any case, the demo is now available upon request for all interested researchers. Below is the gameplay video shared by John Romero six years ago.