Super Mario Evolution
Original title: Super Mario Bros.
Platform: Nintendo Entertainment System
Region: USA (Update Hacks)
Media: Cartridge
Controller: NES Gamepad
Genre: Platformer 
Gametype: Hack
Release Year: 2004
Hacked by: mikamashi
Version: 2.0
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This is a hack found on a Japanese site which does a pretty good job of hiding the fact it's a regular Mario Game. It changes the music, graphics, and level structure to be a bit unlike your normal Mario game. While it is relatively short, it is pretty fun while it lasts.

http://www.romhacking.net/hacks/188/