I previously described tool-assisted speedruns in this post. To summarize, this breed of speedrunners use special emulation tools which alter the speed of the game; anything from slowing the game down to play it frame-by-frame to rewinding a live game is possible -- the latter mechanic has been adapted into games like Prince of Persia and Braid. Combining these abilities with glitches let the user create a speedrun far faster than any human being playing the game in real-time.
These speedrun is not recorded as a video, but rather a series of button presses timed to the game. These recording can be used to replicate the speedrun on any computer with an emulator capable of reading it. Now, an Instructables member named pjgat has taken speedruns into the real world. Using an Arduino board wired into the controller, the speedrun's button presses are sent directly into the NES hardware. The game is in no way modified; there's just a robot at the wheel.
As you can see by the comments, there is some talk about this being a hoax. Most of the weirdness can be attribute to faulty collision detection -- it is, in fact, a game from 1985, a commenter helpfully points out -- but I'm still not sure why the NES boots so fast. So here is the video:
...and a Super Mario Bros. 3 which is slightly faster than the one mentioned in the previous post: