A fascinating Super Mario Bros 3 glitch has been found that skips ahead to the game's ending with Princess Toadstool. The setup may seem complex at first, but completing SMB3 in mere minutes is rather incredible (and controversial).
After nabbing the first two warp whistles and traveling to World 7, a glitch in World 7-1 can have Mario rescuing the Princess in just over three minutes of playtime! (Imagine if all girls got off that quickly...)
It doesn't work every time because it's difficult to line everything up. Most of the Koopa shells need to be placed perfectly, to the pixel. (This trick also cannot be completed in the Super Mario All-Stars version)
I found the following videos helpful...
The first video is 10 minutes long - And even if your mind is blown by all the technical details, it's really interesting to see what's happening behind the scenes in the game's code... Which helps to understand why these variables are so important to make the glitch work. The second video is a simple explanation. Third video is a simple playthrough performing the glitch.
Super Mario Bros. 3 - Wrong Warp (10:06) by Retro Game Mechanics Explained
Super Mario Bros. 3 - How to do the 7-1 wrong warp glitch! (Easy setup) (7:17) by Taven Webb
(video is taken from handheld device, but setup is easy, as advertised)
Completing The SMB3 Wrong Warp Successfully (3:57) by Antique Girl
A collection of notes and screenshots from a few successful attempts:
Back to the start of the level to find the first Koopa. This value is relatively simple to set. Because the final pipe glitch is easier to perform with small Mario, Super Mario holds this Koopa shell right beneath this pipe.
But if everything lines up, and the correct values are in place, Mario returns on screen standing on this block. A simple jump with 'A' can trigger the game into loading the Princess room and end-game sequence, plus an arsenal of P-Wings for your efforts.