Dudley Moore

as Dr. Jack Hammond / Chris Hammond

Kirk Cameron

as Chris Hammond / Dr. Jack Hammond

Margaret Colin

as Ginnie Armbruster

Catherine Hicks

as Dr. Amy Larkin

Patrick O'Neal

as Dr. Larry Armbruster

Sean Astin

as Clarence / Trigger

Camille Cooper

as Lori Beaumont

Micah Grant

as Rick Anderson, Lori's Boyfriend