Neil Gaiman and the late Sir Terry Pratchett co-wrote Good Omens—about a young boy and the Antichrist who were switched at birth—27 years ago, which has given fans 27 years in which to ruminate what a movie or TV series of the novel would look like. Gaiman warns that the actual production will “probably not” resemble the version in your head.
Gaiman recently wrote on Tumblr that the characters that fans visualize are different from what he pictured—and that characters he visualized are different than even Pratchett pictured. (Unless you pictured David Tennant and Michael Sheen, in which case you are 100 percent correct.)
"Good Omens has been unillustrated for 27 years, which means that each of you gets to make up your own look for the characters, your own backstories, your own ideas about how they will behave ...
“You might like it – I really hope you will – but you don’t have to. You can start watching it, decide that you prefer the thing in your head, and stop watching it.”
In what is likely one of the most reasonable plea for tolerance from fans, Gaiman said that your “headcanon,” that is, the images in your head that you personally treasure, are as valid as anything you will see on screen.
As Gaiman said, “[N]obody is ever going to take them away from you.”
In other words, if you don't like Tennant and Sheen, you are personally welcome to picture Chris Hemsworth and Chris Evans. Or Kate McKinnon and Leslie Jones. Your imagination is as important as his.
Here’s hoping that Gaiman’s laid-back approach to fan angst makes fandom a less angsty place.
You can read his full statement here.