The six-part television adaptation of Neil Gaiman and Terry Pratchett's novel is currently in production.
It will be released by Amazon Prime Video in more than 200 countries in 2019 and will be followed by a run on BBC Two in the United Kingdom.
"Once we had finished writing Good Omens, back in the dawn of prehistory, Terry Pratchett and I started plotting a sequel," Gaiman said in a statement Monday.
"There would have been a lot of angels in the sequel. When Good Omens was first published and was snapped up for the first time by Hollywood, Terry and I took joy in introducing our angels into the plot of a movie that was never made. So when, almost 30 years later, I started writing Good Omens for TV, one thing I knew was that our angels would have to be in there. The leader of these angels is Gabriel. He is everything that Aziraphale isn't: he's tall, good-looking, charismatic and impeccably dressed. We were fortunate that Jon Hamm was available, given that he is already all of these things without even having to act. We were even more fortunate that he's a fan of the books and a remarkable actor."
"I read Good Omens almost 20 years ago," Hamm added. "I thought it was one of the funniest, coolest books I'd ever read. It was also, obviously, unfilmable. Two months ago Neil sent me the scripts, and I knew I had to be in it."