In late 2011, Andrew Gardikis set a record for a "speed run" on Super Mario Bros. -- this means he played through the entire game as quickly as possible (yes, he used the warp tubes). For that 2011 run, Gardikis calculated his time at 4:58.898, or just under five minutes (he's calculating down to the frame level).
Then on January 14, 2013, Gardikis published a new video, in which he broke his old record by 0.1 seconds. In the new video, he put the old run in a little window inside the new run, so you can see how similar his pattern is -- he plays with uncanny timing, jumping at almost exactly the same times (with a few goof-off jumps at nonessential points). Because both audio tracks are included, you can hear how similar the two runs are.
At times one run gets slightly ahead of the other, but they end up syncing up due to the 21 frame rule (oversimplified explanation: when the game goes to a black screen or other such transition, it effectively rounds to the nearest 21-frame boundary, thus effectively re-syncing the clock).
Now, I want you to think back to playing Super Mario Bros., and all the times you died on the dumb water levels. Think about all those times you fell in a pit, and what an achievement it was to finally arrive at the final level after hours of play. Now watch Gardikis demolish the game in five minutes.
Gardikis holds other speed records (many of them tool-assisted). On SMB he can apparently do the whole game without warp tubes in 19:40 (!), and he gets major bonus points for sitting through more than 22 minutes of "Yo! Noid," mentioned in my opus 6 Obscure Facts About the Noid.