The free add-on adds a ton of unique content.
A dedicated Super Mario 64 fan, calling himself Skelux, has released a complete modification for the Nintendo 64 classic.
Over a year in the making, the project is a full-featured expansion to the precedential Super Mario 64, and includes more than 30 original areas and 120 Power Stars to collect. In addition, it boasts new music and new objects for Mario to interact with.
The video accompanying the release shows large, colorful levels, many of which bear some resemblance to those in the Super Mario Galaxy games. The mod repurposes the assets, basic aesthetic, and enemies of the original (Goombas, Chain Chomps, cannons, Metal and Wing Caps, etc.) but tosses it all into an original and enticing package.
The mod is available for download on this YouTube page (along with more videos of gameplay and a partial DS port of the add-on), as well as the Google Site for the project, and requires a ROM of the game to run.