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

Robin Williams

Dennis the Dog (voice)

John Cleese

Chief Alien (voice)

Terry Gilliam

Nasty Alien (voice)

Eric Idle

Salubrious Gat (voice)

Terry Jones

Scientist Alien (voice) / Van Driver

Michael Palin

Kindly Alien (voice)

Judy Loe

Canteen Lady

Alexa Davies

Sandwich Girl

Professor Brian Cox

Self

James Kermack

Policeman

Brenda Emmanus

Reporter

Neville Phillips

Author

Ronan Summers

Security Man

David Annen

Newsreader

Mairi McHaffie

Newsreader

Gavin Scott

Newsreader

Jud Charlton

Mortician

Lennon Clarke

Bank Robber

Marat Khairoullin

Zombie (uncredited)

Jorge Leon

Celebrity (uncredited)

Lockhart Ogilvie

Ray Worshiper (uncredited)

Tony Pankhurst

Father (uncredited)

Alan Yentob

Man at Party (uncredited)