Headcanon: David Tennant and Michael Sheen totally exist in the Good Omens universe. Their resemblance to a certain angel and demon is completely casual, but that doesn’t stop Aziraphale and Crowley from crushing hard on them.
When “Bring Young Things” comes out, Crowley nearly has a heart attack every time Miles is on screen. Aziraphale goes to see David Tennant act in Shakespeare plays and very nearly discorporates.