I often wondered what Super Mario 64 2 would look like, until I found out there was a full hack out there with 38 stars. I wasn't aware of any 3D Mario hacks.
38 stars in about 10 new levels
A Day/night cycle replacing (most) act selectors
Choose to play as Mario or Luigi
Modified enemies, objects and bosses (too many to list!)
Custom music, including one original song (the town “night” music)
A new final boss fight