Devs Play – Hacking a Legend of Zelda ROM [video]

In a similar vein are videos from the speed-running community. Linked below is a video of an Ocarina Of Time speed-run where the guy explains a bit of what it's all about. The level of reverse-engineering is impressive.

https://www.youtube.com/watch?v=0M7IINwTFVw

But this is the first time I've heard of somebody hacking the game to highlight different aspects of the gamelplay, which is pretty cool.