According to Christian Bale, much of the movie was improvised. So during the shooting of the film, he noted to writer and director David O. Russell, "You realize that this is going to change the plot greatly down track." To which Russell replied, "Christian, I hate plots. I am all about characters, that's it."
David O. Russell stated that Robert De Niro didn't recognize Christian Bale on the set, even after they were introduced to each other. De Niro pulled Russell aside, pointed to Bale and asked who he was. First De Niro didn't believe it was Bale, but after Russell convinced him of that De Niro noted, "Wow, he looks really different", and nodded his head as a sign of approval. Russell then had to re-introduce the two, now that De Niro knew who Bale was.
There are over two hundred visual effects shots in the film, most of which were comprised of removing modern cars and buildings on-location that weren't around in 1978 to 1980.
The film is a fictionalized telling of the Abscam (short for Abdul 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.
Carmine Polito was based on the real-life Mayor of Camden, New Jersey, Angelo Errichetti, who was snared in the Abscam scandal, and served three years in prison on bribery charges. He died at age 84, in May 2013, only a few months before this movie was released.