Johnny breaks his foot attempting to skateboard down Hospital Hill. The girls give him a robotic foot as they try to fix his regular foot in a yet-to-be-tested healing chamber, resulting in a growing disaster that they must stop before it stomps out Porkbelly! Evil Villain The Tickler discovers that the way to destroy Johnny Test is by eliminating the people who supply him with all his inventions-Susan and Mary. Johnny needs a crash course in evil to defeat him and takes the advice of all the villains in town to save his sisters.