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 is pursued by three bounty hunters sent by Vilgax to steal the Omnitrix.

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

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.