Warner Bros. has hired Alec Baldwin to appear opposite Joaquin Phoenix in its “Joker” origin film, playing the role of Thomas Wayne, the father of Batman, a.k.a. Bruce Wayne.

Variety first reported that Phoenix was in talks to play the Clown Prince of Crime. As soon as his deal was finalized, the studio gave the greenlight to a September start date with a budget in the moderate $55 million dollar range.

Todd Phillips (“The Hangover” franchise) is on board to co-write and direct. Jared Leto will not appear in this Joker film. Leto played the Joker in 2016’s “Suicide Squad” and is expected to be back for the “Suicide Squad” sequel, along with another standalone Joker movie that will be separate from Phoenix’s Joker project.

Scott Silver is a co-writer with Phillips on the Joker origins film, which will delve into how the Joker became a criminal mastermind. Robert De Niro is portraying a talk-show host who plays a part in driving Phoenix’s character to go mad. Zazie Beetz and Marc Maron are also starring.

The Thomas Wayne character was introduced in 1939 in Detective Comics as part of the story of Batman’s origins. He was a physician and philanthropist to Gotham City who was murdered with his wife in a street robbery, serving as the inspiration for his son Bruce Wayne to fight crime as Batman.

Baldwin is up for an Emmy for outstanding supporting actor in a comedy series for playing Donald Trump on “Saturday Night Live” after winning the category last year. Baldwin can be seen in “Mission: Impossible – Fallout” and Spike Lee’s “BlacKkKlansman.”

Baldwin is repped by CAA. The news was first reported by Deadline.