The 52-year-old was set to star as Henry Allen - the father of Barry Allen and his titular alter-ego - in the DC Extended Universe movie but has now left the production due to scheduling conflicts with the Apple drama, which also stars Jennifer Aniston and Steve Carell.
While Billy has left, Maribel Verdu has been cast as Barry's mother in the movie.
Kiersey Clemons has recently joined the cast as Iris West, who is set to be a romantic interest of The Flash.
Meanwhile, four years ago Billy revealed he was unsure of when production would start, due to Ezra's hectic schedule.
When asked if he knew when "The Flash" would start filming, Billy said, "I don't. It's unclear at the moment. I think, Ezra's schedule ... Ezra's a busy man, he's very popular and excellent."
And it wasn't just the busy schedule of Ezra that had a hand in delaying the movie, as the production suffered another setback when the movie's director Rick Famuyiwa - who had been brought in to replace Seth Grahame-Smith - quit due to creative differences between himself and Warner Bros. studios.
Andy Muschietti is now directing the movie, from a script written by Christina Hodson.