World 9 glitch

The World 9 glitch is a glitch triggered in a pirated port of Super Mario Bros.: The Lost Levels´ FDS version, the pirated port being ported to the NES in question.

Description
The glitch was discovered by MadeForReleasio Toad on a ROM hack of the same pirate that is edited to be a Releasio type game. If a FDS (the original game´s) savestate of World 9-1 to 9-4 is loaded, it will load in a glitched level that has a high chance to either crash or softlock the game. The main focus of the video is on 9-4, a very odd level. Also, Mario will become grey or black most of the time upon loading a FDS savestate.

Level 9-1
A glitched level with plenty of cloud blocks and glitchy blocks that you can pass through. Completing the level or going in a certain pipe crashes the game.

Level 9-2
This level immediately crashes upon entering it, and the only thing you can see (aside from Mario and the ground) is a Piranha Plant in a pipe.

Level 9-3
Not much is discussed about 9-3 in the video.

Level 9-4
Level 9-4 is a seemingly randomized level that takes place in a black void background and some glitchy background blue and red-colored tiles occasionally. The terrain (etc. ground and blocks) is always the same, but enemy placement is random, and everything can spawn in the level presumably, though MadeForReleasio Toad reports on all of his times on Level 9-4 he never saw a single Hammer Brother. 9-4 has a wide range of things that it will spawn, ranging from just Goombas to fire bars to Bowser and even glitched variations of Peach´s sprite. It is possible to glitch past the flagpole at which point the game glitches out more and spawns a few enemies, then the ¨Past the Flagpole¨ glitched graphics from the original game and the game the original game was a sequel to, occasionally spawning Bowser in, but this cycle endlessly repeats.

Why does this glitch happen?
Presumably the glitch happens due to the pirates removing World 9 from the pirated port and also partially from loading a FDS savestate. Worlds A-D work fine however and World 8-4 crashes upon being beaten due to it trying to save to disk, so World 9-1 is not legitimately accessible without savestates.

Credits
MadeForReleasio Toad (presumably helped with the ROM hack and creator of the video), and the pirates that created the original game for, well, creating the original game.