The ability to practically program code into Super Mario World through the use of glitches opens up all sorts of possibilities, some definitely more bizarre than others. Just look toward speedrunner and tinkerer Sethbling, who managed to turn Mario into a Flappy Bird clone.
Sethbling injected the code using un-modded SNES hardware, making pixel-perfect moves to write the necessary code into memory. While such projects have been done before with computers and pre-recorded inputs, this is the first reported time such a feat has been accomplished under human handpower.
Overall, the injection took about an hour to complete, and Sethbling takes the time to thank others responsible for creating the code and exploits. The whole process is honestly a little complicated to explain, but he does a good job laying it all out in his rundown video.
You might also remember Sethbling for holding a Super Mario World completion record not too long ago through use of a "credits warp" glitch. Who knows what more crazy exploits and modifications can be found through messing with Mario.