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)

Terry Jones

Scientist Alien (voice) / Van Driver

Michael Palin

Kindly Alien (voice)

James David Robinson

Steve

Judy Loe

Canteen Lady

Alexa Davies

Sandwich Girl

Ellie Green

Lavender

Professor Brian Cox

Self

James Kermack

Policeman

Brenda Emmanus

Reporter

Neville Phillips

Author

Edward Fisher

Mr. Eriksson

Simon Coleman

Police Inspector

Ronan Summers

Security Man

David Annen

Newsreader

Mairi McHaffie

Newsreader

Gavin Scott

Newsreader

Richard Suchet

Newsreader

Christopher Chesser

Documentary Voice (voice)

Margarita Doyle

Alien Computer Voice (voice) / Señorita Lopez

Jud Charlton

Mortician

Lennon Clarke

Bank Robber

John Bedford

Ray Worshiper

Marli Bland

Ray Worshiper

Basia Forrest

Ray Worshiper

Liliana Gane

Ray Worshiper

Lorna Lacey

Ray Worshiper

Debbie J. Nash

Ray Worshiper

Christian Palmer

Ray Worshiper

Zara Sorensen

Ray Worshiper

Chris Weeks

Ray Worshiper

Robert Jones

Pink Policeman

Chris Daniels

Pink Policeman

Charlie Richards

Pink Policeman

Samuel Timlett

Baby

Lasco Atkins

Party Guest (uncredited)

Hannah Blamires

Photographer (uncredited)

Stuart Budd

Passerby (uncredited)

Marat Khairoullin

Zombie (uncredited)

Jorge Leon

Celebrity (uncredited)

Tremayne Miller

Book Launch Guest (uncredited)

Lockhart Ogilvie

Ray Worshiper (uncredited)

Tony Pankhurst

Father (uncredited)

Alan Yentob

Man at Party (uncredited)