Youtube user agwawaf has succeeded in "beating" Super Mario Bros., Super Mario Bros. 2, Super Mario Bros. 3 AND Super Mario Bros. The Lost Levels at the same damn time.
How is this possible? agwawaf's run-through(s) is tool assisted, meaning that he used 4 different emulators running simultaneously to play all four games with only one device, be it a keyboard or controller. The emulator(s) allowed him to slow down the gameplay to frame-by-frame and/or rewind the action of all or each game individually, thus preventing little Mario from meeting any untimely demise, regardless of which game.
What you're watching is essentially 4 NES games being played to completion with the same list of commands. Pretty impressive, but be warned that this thing wreaks havoc on one's ADD. I think I started frothing from the mouth around minute 5.
Basically, agwawaf clearly had way too much time on his hands and this task would have been impossible to duplicate without emulators, macros, and other tools. But there's nothing wrong with absorbing 13 minutes of pure nostalgia. On crack.