A bizarre glitch in Super Mario World, and an incredible amount of patience, and the SNES classic is transformed into Flappy Bird.
It's incredible to watch SethBling in action. Once the glitch (triggered by giving Mario too many power-ups) is active, machine code can be arbitrary rewritten in memory by carefully moving Mario around. This code can, ultimately, be executed. The process takes an hour of careful pixel-perfect actions in the game world, which becomes stranger and more nightmarish as Mario's universe-editing rituals proceed.
Welcome to the weirdest, most painful, most existentially-nightmarish IDE—and a reminder that our own reality is probably an abandoned simulation waiting for someone to take too many power-ups and turn it all into a sadistic casual game.