Simon Pegg

Neil

Kate Beckinsale

Catherine

Sanjeev Bhaskar

Ray

Rob Riggle

Grant

Robert Bathurst

James Cleverill

Eddie Izzard

Headmaster

Joanna Lumley

Fenella

Marianne Oldham

Rosie

Emma Pierson

Miss Pringle

Meera Syal

Fiona

Mojo

Dennis the Dog

Robin Williams

Dennis the Dog (voice)

John Cleese

Chief Alien (voice)

Terry Gilliam

Nasty Alien (voice)

Eric Idle

Salubrious Gat (voice)