I thought finishing Super Mario Bros. 3 with my dad over the course of a week when I was a little girl was impressive, but this speedrun clocking in at 2:54:98 has forever shamed me.
Of course, it lessens the pain a bit to know that this isn't exactly a "legitimate" time -- it's a tool-assisted video from TASVideosChannel that uses a pipe glitch to allow Mario to make his way to Peach in world 7-1 in record time.
Lord Tom and Tompa explain their methods in brief on the YouTube video description: "This run gets to World 7-1 as quickly as possible to perform the glitch, and some unusual moves are done with enemy spawns and positions to get the glitch to work. [...] There are also author subtitles provided with the emulator movie file and primary encode to explain some of the key differences in this run."
I salute thee, Lord Tom and Tompa. I'm lucky to get my playthroughs down to a few hours. For more information on how this run was completed, check out the video's archive page on the TAS Videos site.