It may not be the speediest of speed runs. It may not dazzle with its exploitation of glitches. But this Super Mario Bros. speed run is notable because the player is also simultaneously beating Super Mario Bros. 2, Super Mario Bros. 3 and Super Mario Bros. The Lost Levels.
This is the work of Japanese player "agwawaf" who says he "completed the four games with one input." That's four games finished with one controller in under 14 minutes—in part thanks to "tool assisted" gameplay, meaning "agwawaf" likely played the four Super Mario Bros. games with the help of an emulator that slowed gameplay and/or let him stitch together multiple attempts to get the job done.
This is not the Japanese Mario expert's only multi-game accomplishment. User "agwawaf" has performed similar feats with Mega Mans 1 through 6. Watch that one if you'd really like to have your senses scrambled.
Even with that concession... damn.
More crazy tool assisted speed run video's at agwawaf's YouTube channel.