The first rom hack I played for co-op was quite entertaining throughout all the levels of the game, with a simple design but perfect for people who are just getting into Mario 64 rom hacks.
My only complaint would be that there was a star that required a wall kick that wasn't easy at all (or at least my friends and I had a hard time doing it).
Other than that, it was perfect. I recommend it if you want to play a simple, short rom hack with friends.