The Mad Dog cheerleaders (and mascot) are off to Cheer Camp. But when a plumbing problem prevents them from holding it at a community college, they're forced to relocate to the newly-renamed Camp Gottagrin. The situation gets worse when Kim discovers she's rooming with Bonnie, while Ron's roommate is the now-human Gil, who's also his football team's mascot.
Lake Wannaweep has been detoxified, but when Gil finds a still-toxic grotto, he dives in, becomes Gill, and starts wreaking havoc. Ron then realizes that the only way to defeat a swamp mutant ... is to become one.