On Roy's Conveyor Castle (Rock-Candy Mines-Boss Castle) there is a secret entrance or otherwise known as a "back door" leading into the castle from a secret entrance not able to be accessed any other way, other than hacking, leading directly to the door to the battle with Roy. The only way to unlock it's accessibility is to find the secret exit to Walking Pirhana Plants! (Rock-Candy Mines-5) and push the red button unlocking the way into the "back door" after completing Screwtop Tower (Rock-Candy Mines-Castle2) . (url=http://m.youtube.com/watch?v=BbMWKOOcgX0)This is a video showing you how to unlock the secret exit to Walking Pirhana Plants! (Rock-Candy Mines-6)(/url) .
Before every boss you must step through a door to the battle. Before the door there is a hidden ? Block that you can hit and will give you a power. They are beside the wall so just line up with each wall and jump to hit the ? Blocks. They are helpful tools for the upcoming boss.