Superfast Mario Bros. is a romhack of the original Super Mario Bros. game which can only be described as chaotic experience. The game speed has been jacked up extremely high, as well as framerules being reduced to 1 frame rather than 21, transitions are instant, and yet the game is still somehow playable. Not that it matters in a TAS setting that is.
eien86 improves on the previous run by 4 seconds thanks to a couple of new strategies and the use of a program called JaffarPlus, which found lots of optimizations.
WARNING: This hack can be very visually glitchy and occasionally have moments of flashing lights which may be uncomfortable to some viewers.
Watch a resync of this run being played back on a real console.