The series is a prequel, featuring the high school years of Flint Lockwood, the eccentric young scientist in the films. In his adventures, he will be joined by Sam Sparks, a new girl in town and the school's "wannabe" reporter, along with Flint's dad Tim, Steve the Monkey, Manny as the head of the school's audiovisual club, Earl as a school gym teacher, Brent as a baby wear model, and Mayor Shelbourne, who wins every election on the pro-sardine platform.
Jenny, aka XJ-9, is a super-powered robot with a super-sensitive teenage heart. Her primary function is protecting the planet from disaster, but – like all teenagers – she has her own ideas about how she would like to live her life. Bored with being a superhero, Jenny wants to do something really exciting – like go to high school!
Dexter, a boy-genius with a secret laboratory, constantly battles his sister Dee Dee, who always gains access despite his best efforts to keep her out, as well as his arch-rival and neighbor, Mandark.
Jimmy Neutron is the smartest kid in town. As a genius, Jimmy thinks most things can be solved with the invention of a new gizmo. But Jimmy usually takes the easy way out, and his backfiring gadgets result in comedic adventures.