This is a glitch that will only work "on version 1.1 of the Famicom version of the game," the official description states. "Don't try this on the NES because it won't work."
This knocks most of us out of being able to try this at home, but the video explaining what’s happening here and why it works is still fascinating, if a bit technically demanding to follow.
"Shout-outs again to Sockfolder for discovering the glitch and writing this code," the description says. "Sockfolder is a brilliant glitch hunter and programmer who does similar stuff for other things. If you're interested, follow him on Twitter at https://twitter.com/sockfolder and on Twitch at https://www.twitch.tv/sockfolder."
To boil it way down, this exploit relies on your ability to understand what the game is doing at exactly the right moment and why, while also taking advantages of the limitations of the Famicom.
The video explains an esoteric process in a manner that’s relatively easy to follow, so enjoy!