Christian Bale was cast in the lead role but due to scheduling conflicts he dropped out and was replaced by Bradley Cooper with Jeremy Renner taking over Cooper's old role. After Bale's schedule cleared up he rejoined the project in the same role while Cooper reverted to playing the FBI agent and David O. Russell wrote the character of Carmine Polito for Renner.
The film is a fictionalized telling of the Abscam (short for Arab scam) scandal of the late 1970s and early 1980s, an FBI operation that began as an investigation of trafficking in stolen property, but was later expanded to include political corruption.
The character played by Shea Whigham discusses gambling in Atlantic City, and his character in Boardwalk Empire (2010) is also from Atlantic City. (Co-star Jack Huston also appears in "Boardwalk Empire".)
Sydney puts a colorful jacket on Irving in the dry cleaners. You can see clearly that when he hugs her from behind he still has the solid color blazer on.
When Irving and Carmine are outside The Plaza Hotel you can clearly see the Bergdorf Goodman Men's Store across the street on the east side of Fifth Avenue. The Bergdorf Mens store did not move there until 1990.