Average kid, ten year old Ben Tennyson, his Grandpa Max and his cousin Gwen's summer of adventure takes an odd turn when Ben discovers a watch like object that has been jettisoned from alien spacecraft high above the Earth.

Ben must fight Dr. Animo, a crazed scientist who has a DNA-altering device.

Ben has his hands full with a giant sea monster and an evil poacher.

Ben must rescue his aunt and grandfather when they are held hostage by shape-shifting aliens.

Ben accidentally releases creatures made of electric energy and must use his own powers to recapture them.

Ben meets a mutant who can absorb any form of energy and may be after the Omnitrix.

Ben clashes with a female gang member who's become part cyborg.

Ben discovers an evil circus that's headed by a psychic vampire clown named Zombozo.

Ben battles a sorcerer who possesses a number of charms, and Gwen suddenly becomes a superhero when one of the charms falls into her hands.

Ben gets revenge on an amusement-park attendant who said he was too small to go on a ride.

Ben's summer cold causes strange physical changes in his alien personas.

Vilgax tries to get the Omnitrix for himself while Grandpa Max's strange past becomes known, causing a showdown between Vilgax and the Tennyson family.