Simon Pegg

Neil Clarke

Kate Beckinsale

Catherine

Robin Williams

Dennis the Dog (voice)

Rob Riggle

Grant

Sanjeev Bhaskar

Ray

Joanna Lumley

Fenella

Marianne Oldham

Rosie

Suzy Eddie Izzard

Headmaster

Robert Bathurst

James Cleverill

John Cleese

Chief Alien (voice)

Judy Loe

Canteen Lady

Professor Brian Cox

Self