A PhD student in Artificial Intelligence at Imperial College in London has created AI control for Mario to go through levels in the style of his old 2-D platforming games (like Super Mario World on the SNES). His AI Mario can run through the level, dodge enemies, pick up koopas, throw fireballs, and jump from platform to platform. It's pretty neat stuff, and he has videos posted of his AI Mario in action. In his videos you can actually see the paths that the AI considers drawn in red overlaid on the game screen.

The source code is also available if there are any programmers out there that want to tinker with his work.

Mario AI project