Matthew Broderick as John Brown / Inspector Gadget / Robo Gadget

Rupert Everett as Sanford Scolex / Dr. Claw

Joely Fisher as Brenda / Robobrenda

Michelle Trachtenberg as Penny

Andy Dick as Kramer

Cheri Oteri as Mayor Wilson

Mike Hagerty as Sikes

Dabney Coleman as Chief Quimby

D.L. Hughley as Gadgetmobile (voice)

René Auberjonois as Artemus Bradford

Frances Bay as Thelma

Mr. T as Himself

Richard Kiel as Famous Big Guy with Silver Teeth

Richard Lee-Sung as Famous Villain with Deadly Hat

Bobby Bell as Famous Identifier of Sea Planes

Hank Barrera as Famous Native American Sidekick

Keith Morrison as Famous Assistant to Dr. Frankensomething

John Kim as Son Before Second Son

Jesse Yoshimura as Bane of the Bumbling / Robobrendaerobics Group Member

Aaron Meyerson as Aaron Meyerson

Cliff Emmich as Out of Control Bus Driver

Richard Penn as Fantastic Doctor

J.P. Manoux as Mayor's Sychophantic Assistant

Brian George as Sore Guru

Alexander Witt as Wet, Green Businessman

E.J. Callahan as Hot Dog Vendor

Chad Parker as Assistant Car Thief

Frank Masi as Period Photographer

Mary Chris Wall as Snoopy News Anchor

Linda Cevallos as Showgirl

Loralyn Peterson as Showgirl

Andy Heyward as Mr. D.I.C. - Party Guest

Don Adams as Brain (voice)

Danny Nero as Police Officer (uncredited)