A bug has been found in Super Mario Bros. based on the so-called ACE (Arbitrary Code Execution), a technique that allows you to execute your own code inside the game. This is a serious event, because for decades it was believed that the original "Mario" had been taken apart and there were no more secrets. The new discovery shows that even such a well-studied game can hide surprises.
Previously, ACE was used in other projects, which allowed, for example, to skip entire levels or completely change the way the game works. In the case of the first part of Super Mario Bros. this is something new and potentially revolutionary. While the find is not being used in speedruns to its full potential, players are unanimous: this could open the door to new records and other ways to complete the game.
This is another proof of the franchise's phenomenon. Nintendo designs its hits to be full of secrets and hidden mechanics.