Tim Allen as Jack Sheppard

Courteney Cox as Marsha Holloway

Chevy Chase as Dr. Grant

Spencer Breslin as Tucker Willams / Mega-Boy

Kevin Zegers as Connor Shepard / Concussion

Kate Mara as Summer Jones / Wonder

Michael Cassidy as Dylan West / Houdini

Ryan Whitney as Cindy Collins / Princess

Rip Torn as Larraby

Cornelia Guest as Cindy's Mom

Ashton Moio as Halloween Bully

Hunter Aarniokoski as Prince

Thomas F. Wilson as Dylan's Teacher

Ridge Canipe as Mean Bully

Danny McCarthy as Meaner Bully

David L. Lander as Wendy's Employee

Lauren Sánchez as Reporter

Willie Garson as Dick

Jane Hajduk as Researcher Taylor

Tommy Chang as Martial Arts Instructor

Zoe Doyle as Researcher

Tim Nasiopoulos as Large Agent

Deanna DeLisle as Cheerleader

Meg Anderson as Cheerleader

Kendra Rose Montagna as Cheerleader

Aaron Abrams as Corporal Lipscombe (uncredited)

Stacey Alfano as Stefanie (uncredited)

Nick Baga as Fat Swimmer (uncredited)

Alexis Bledel as Ace (uncredited)

Darryl Dinn as Lab Researcher (uncredited)

Allison Gordon as Girl with Big Hair (uncredited)

Sadey Paige Nifong as Kid In Pool (uncredited)

Andrea Savo as Carmen / Big haired Latina (uncredited)