Mike Myers as The Cat

Dakota Fanning as Sally Walden

Spencer Breslin as Conrad Walden

Kelly Preston as Joan Walden

Alec Baldwin as Larry Quinn

Amy Hill as Mrs. Kwan

Sean Hayes as Mr. Humberfloob / Fish (voice)

Danielle C. Ryan as Thing One

Taylor Rice as Thing One

Brittany Oaks as Thing Two

Talia-Lynn Prairie as Thing Two

Dan Castellaneta as Thing One / Thing Two (voice)

Victor Brandt as Narrator (voice)

Daran Norris as Announcer

Frank Welker as Nevins (voice)

Clint Howard as Kate the Caterer

Paige Hurd as Denise

Steven Anthony Lawrence as Dumb Schweitzer

Paris Hilton as Female Club-Goer

Candace Brown as Secretary

Stephen Hibbert as Jim McFinnigan

Roger W. Morrissey as Mr. Vompatatat

Norman Fessler as Mailman (uncredited)

Danny Nero as Man in Street (uncredited)

Brian George as Sanjay (uncredited)