In the Royal Raceway in the Star Cup, you can jump through Peach's Castle. Drive quickly to the bridge which leads to the main door (or, main door for Mario 64). Go to the right of it and press R to jump over the railing. Look at the picture for a good spot to jump from. If you were driving quickly enough, you will go through the castle and see a beautiful pink sky... However, you won't be able to savor the view for long. You will crash down and Lakitu will grab you and put you back on land.