Simon Pegg

Character: Neil Clarke

Kate Beckinsale

Character: Catherine

Robin Williams

Character: Dennis the Dog (voice)

Rob Riggle

Character: Grant

Sanjeev Bhaskar

Character: Ray

Joanna Lumley

Character: Fenella

Marianne Oldham

Character: Rosie

Eddie Izzard

Character: Headmaster

Robert Bathurst

Character: James Cleverill

John Cleese

Character: Chief Alien (voice)

Judy Loe

Character: Canteen Lady

Brian Cox

Character: Self

Meera Syal

Character: Fiona

Emma Pierson

Character: Miss Pringle

David Annen

Character: Newsreader

Mairi McHaffie

Character: Newsreader

Gavin Scott

Character: Newsreader

Terry Gilliam

Character: Nasty Alien (voice)

Eric Idle

Character: Salubrious Gat (voice)

Terry Jones

Character: Scientist Alien (voice) / Van Driver

Michael Palin

Character: Kindly Alien (voice)

Alexa Davies

Character: Sandwich Girl

Neville Phillips

Character: Author

Ronan Summers

Character: Security Man

Jud Charlton

Character: Mortician

James Kermack

Character: Policeman

Lennon Clarke

Character: Bank Robber