Main •
Ricky Ullman as Philip "Phil" Diffy, a teenager from the year 2121 who adjusts to life as a high school freshman (Season 1) and sophomore (Season 2) in the present day. He becomes best friends and eventually romantic partners with Keely. •
Amy Bruckner as Pimilla "Pim" Diffy, Phil's mischievous younger sister, a
middle school student with a tendency toward scheming and megalomania. •
Craig Anton as Lloyd Diffy, the family patriarch and an engineer from 2121 who spends the series attempting to repair the time machine. •
Lise Simms as Barbara "Barb" Diffy, Phil and Pim's mother, who enthusiastically but awkwardly adapts to 21st-century domestic life. •
Alyson Michalka as Keely Teslow, Phil's next-door neighbor, best friend, and eventual girlfriend, an aspiring news reporter who is the only outsider to know the Diffys' secret.
Recurring •
J. P. Manoux as Curtis, a Cro-Magnon caveman who stowed away in the Diffys' time machine, and as Vice Principal Neil Hackett, the series' primary
antagonist, who suspects the Diffys are hiding something. •
Kay Panabaker as Debbie Berwick (Season 1), Pim's relentlessly cheerful classmate who considers Pim her best friend. •
Brenda Song as Tia Fedichelli (Season 1), Keely's popular best friend, who departed when Song joined the cast of
The Suite Life of Zack & Cody. •
Evan Peters as Seth Wosmer (Season 1), Phil and Keely's nerdy friend. •
Spencer Locke as Candida Scobel (Season 2), a popular girl who antagonizes Pim. •
Brandon Smith as Li'l Danny Dawkins (Season 2), a younger student with a persistent crush on Pim. • Juliet Holland-Rose as Olivia "Via" (Season 2), an English transfer student who replaces Tia as Keely's close friend. • Michael Mitchell as Owen (Season 2), Phil's laid-back friend who replaces Seth. •
Joel Brooks as Mr. Messerschmitt (Season 2), Phil and Keely's demanding teacher. == Episodes ==