Years after its release, I thought I'd seen everything you could do in SNES classic Super Mario World.
But now, someone has programmed Super Mario World from within the game - while playing it - so it transforms into a completely different and entirely functioning other game, Flappy Bird.
The video below shows SethBling pull off the feat in under an hour. That's the time it takes for him to open up an exploit in Nintendo's code and begin turning the game, piece by piece, into something else entirely.
I love the video below because it shows off exactly how the method is achieved (by tricking the game into thinking the player is using a power-up that doesn't exist) but also demonstrates how ridiculously fiddly this method is (you then have to stand in pixel-perfect places to save new code into the game's memory).
Early parts of the code modification allow the user to see Mario's exact pixel position in a level - tools which will then allow for further programming.
The final part of the process is entering in Flappy Bird's code, line by line, using the position of Mario in the level and securing the code by picking up mushrooms.
And the moment where it all transforms? Well, you should just watch: