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[edit] Dr. Vile

Dr. Vile can only be reached after defeating at least two bosses, and prior to killing Bit and Byte. There are three ways to reach his level:

1. At the start of Volt Catfish's stage, there is a platform that will take you to Dr. Vile.
2. In Blizzard Buffalo's stage, after you enter the small room with two doors, slide down the left side of the first pit you see.
3. In Crush Crawfish's stage, after defeating the mini boss you will see an energy capsule. Walk towards it and you will fall through the floor, discovering a teleportation pad.