For reasons that I’m not going to get into, it was important for us that they were - in a number of ways - visually reminiscent to each other. They have- David and Michael, they normally aren’t in things together because they go up for the same parts.

Neil Gaiman (x)

”But I love the fact that we have them together. When Terry and I were asked who we wanted to play Crowley and Aziraphale, back when the book first came out in 1989/1990, we said: If he was still alive we’d want Peter Sellers playing both parts. And I kind of feel like this is the closest we ever get to that.
They could absolutely- You know, Michael Sheen, when I saw him the other night, he had noticed a line by somebody on Twitter that sort of said was what they like to see was a stage play of ‘Good Omens’ with Michael and David swapping parts each night, playing Crowley and Aziraphale each. And I could see that.”