While in the magic shop Crowley (David Tennant) dons a red fez. Yet another Doctor Who reference as Matt Smith, the 11th Doctor was fond of wearing fezzes because "Fezzes are cool."
Aziraphale talks about the Doctor Who Annual published in 1965. David Tennant, who stars as Crowley in this show, starred as the Tenth Doctor in the revival of Doctor Who (2005- ). Various other actors from the show have also appeared in Good Omens, including David Tennant's father-in-law Peter Davison who was the Fifth Doctor on the original Doctor Who (1963-1989).