Now go and get another 7 stars ( I got them from Lethal lava land and sand land).
Heres where things get tricky. grab the bunn in the basement but don't take the star. Pick him up and go to the door into the basement.
Now go to the door and drop the bunny into the front of the door. Mario should apear inside the door. get down on his knees and turn towards the bunny. Now put it down again.
You should be inside the room with bowsers door in it , with the bunny! Now do the same thing on bowsers door. Here's the link to a youtube video of it http://ca.youtube.com/watch?v=fdA8CjISrrm