Doctor Who's Matt Smith and Sherlock's Andrew Scott are to star in a new one-off play.
The Audience - a sequel to hit West End show The Curious Incident of the Dog in the Night-Time - will see Smith's Doctor pitted against Scott's Moriarty, according to the Radio Times.
Skyfall's Ben Whishaw will also appear as James Bond's gadget-master Q, while Helen Mirren will play the Queen.
The production is part of A Curious Night at the Theatre, a charity gala aiming to raise money for charities Ambitious about Autism and The National Autistic Society.
Smith, Scott, Mirren and Whishaw will appear in specially-filmed scenes, while Jude Law will appear opposite Curious Incident star Harry Treadaway on-stage.
"It is a once-in-a-lifetime opportunity to see all those people in the same story," said director Simon Stephens. "I'm sure a lot of people have fantasised about what would happen if the Doctor did battle with Moriarty."
The Audience will be staged tonight (Monday, July 1) at the Apollo Theatre, London.
Some are born great, some achieve greatness and some have greatness thrust upon them.
The rest of us are a bit crap.