The BBC announced in January that it is partnering with Amazon Prime to produce a comedy drama based on Terry Pratchett and Neil Gaiman's international bestselling book, six hour-long episodes of which are now due to broadcast in 2019.
Today, the corporation confirmed that Tennant and Sheen will take the lead roles in the comedy, as "fast living demon" Crowley and "somewhat fussy angel and rare-book dealer Aziraphale", respectively.
Producers BBC Studios explain: "Aziraphale and Crowley have lived amongst Earth's mortals since The Beginning and have grown rather fond of the lifestyle and of each other. So it's really terrible news for both of them that, if Heaven and Hell have their way, the world will end on Saturday. Next Saturday, in fact. Just before dinner. The armies of Good and Evil are amassing, Atlantis has risen, tempers are flaring. The Four Horsemen Of The Apocalypse are ready to ride. Everything appears to be going according to Divine Plan. Except that someone seems to have misplaced the Antichrist..."
Whilst Terry Pratchett died in 2015 after developing Alzheimer's disease, his co-author Neil Gaiman has adapted their book for the screen, and will act as both show-runner and an executive producer for the series.
Gaiman says of the pair's casting: "If you are looking for actors to play two of the best-loved characters you and Terry Pratchett ever created, then, if you are very lucky and have been very good, you will get Michael Sheen and David Tennant to bring them to life. The best Welsh actor of his generation gets to be an angel, the best Scottish actor of his, a demon.
"Terry and I wrote Good Omens (I like to think it's one of the funniest novels ever written about the end of the world and how we are all going to die) almost 30 years ago. It's strange that it feels more relevant now than it ever did before. I only wish that Terry could be here to see it come to life with such a fantastic team."
Mackinnon, who also acts as an executive producer, says: "Ironically, given that it is a timeless novel, the Good Omens story stretches from the beginning of time to quite near the end of time. I am honoured to be working with Neil Gaiman (and Terry Pratchett in absentia) and directing such a wonderfully prestigious project for BBC Studios and Amazon. I hope to deliver an epic parcel of fun just before Armageddon arrives instead."
Chris Sussman, Head of Comedy at BBC Studios and Executive Producer says: "We're thrilled two actors of the calibre of Michael and David loved the scripts as much as we do, and have signed up to play the leads. This is a very good omen for the project indeed."
Roy Price, Head of Amazon Studios and Prime Video content globally, said: "We could not have hoped for two better suited actors to take the roles in this highly-anticipated show. We look forward to seeing David and Michael make these roles their own, as they are sure to do, and look forward to bringing the show to Prime members around the world in 2019."
Rob Wilkins, Executive Producer and Narrativia Managing Director, says: "I can say with absolute certainty that Terry would be utterly delighted with our Crowley and Aziraphale - both David and Michael were very much in his mind for the roles when we began developing this series for television all those years ago, and I can't believe we've been lucky enough to sign up our dream choices now. I'm so excited that we are this close to filming Neil's brilliant scripts with Douglas at the helm."
Friday 15th September update
Whitehall will be playing Newton Pulsifer aka Newt - an unfulfilled wages clerk turned witch-hunter - and McKean will take on the role of Sergeant Shadwell, the leader of the witch-finder army who sends him on his mission. Miranda Richardson will play Madame Tracy, the psychic medium and part-time courtesan who provides a helping hand to the pair as they try to save the world from Armageddon.
Commenting on his casting as Newt, Whitehall says: "I feel extraordinarily privileged to have been asked to play this part and cannot wait to get started."
Michael McKean adds: "I'm thrilled to join this amazing cast and creative team. I can't think of anyone I'd rather enjoy Armageddon with than Gaiman, Pratchett, Mackinnon and company."