You use the moon jump cheat.
it is not stars it is a world
To get on the castle roof of the castle
Collect 120 stars
By getting a cannon or by winning the fifth castle and then the sixth castle.
Waluigi isn't in that game. The cannon in the castle grounds is unlocked with 150 stars.
To get to the top of the castle on Super Mario 64, there are two ways. The first is to get a running start (running towards the right side corner of the castle), jump on the castle wall, then on the grass, then back on to nearly grab onto the edge, and get on top of the castle. The second way is to get all of the stars, then a cannon will be accessible out on the front part of the castle. Then, climb into the cannon and shoot yourself on top of the castle.
You will need to collect all 150 stars and the cannon in front of the castle should open and then all you have to do is go in the cannon and blast off.
you have to get a cannon from one of the worlds and go in it and boom your there
After collecting all 120 stars, a cannon will appear outside of the castle. Use this cannon to blast yourself to the top of the castle. At the top of the castle, you'll find Yoshi, who will give you 100 extra lives.
You can use the cannon to shoot up to the top of the castle. Yoshi is there in the Nintendo 64 version. After you talk to him, you will have 100 lives.
The cannon in new super Mario bros takes you from one world to another without having to complete the world (ie it shoots you into another world)
Waluigi is not in the game at all.