For Super Mario 64 DS get 150 stars and go in the cannon outside the castle For Super Mario 64 One way to do it is to get 120 stars. Once you've gotten them, go outside and blast from the cannon to roof.
Firstly, there aren't even 150 Stars in Super Mario 64. The DS remake has 150 stars. Secondly, you only need 70 of them (80 on the DS) to actually beat the game. Once you get that number of stars, you will be able to challenge the final boss, and beat the game.