Sites of Interest
Location: Millstone Mayhem
Items: Green Balloon
Walkthrough: The entrance is on the wall to the right below the fifth millstone-riding Gnawty. You need a TNT Barrel to blow it open. You can find the explosive along the way and you may need to carry it til you arrive at the spot.
Judging by the look of this bonus room, it pretty much resembles Bonus Room 4, only that this time, you need to guess which barrel the 2-up balloon will be contained. You need to be quick on this and spot where the balloon could be last seen. Your reward on this will be two extra lives.