Sling Yourself Inside The Castle
To sling yourself in the castle you need to go to the set of small stairs (the stairs on the right leading towards the character room). Stand on the bottom stair and get as close to the wall as possible, then turn around so your back is to the wall. When you think it's ready crouch down and do a back flip. If done right they should slide on the crack and fling you over the railing and down the the 3 star door. This is really hard to get right and takes tons of practice. You can do this with anyone but Yoshi and Luigi are the easiest to do it with.
Added by: Jazzy12x Jan 4th 2010, ID#12992