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.
As the movie states during the opening sequences: "Some of this actually happened". And it did. Christian Bale's character was loosely based on Melvin Weinberg. The FBI employed Melvin Weinberg, a convicted swindler, international con artist and informant, and his girlfriend Evelyn Knight, to help plan and conduct the FBI sting operation. They were both facing a prison sentence at the time and in exchange for their help, the FBI agreed to let them out on probation. Although Weinberg was a previously convicted criminal and had been involved in previous scams, he avoided a three-year prison sentence and was paid $150,000 in concurrence with the operation.
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.
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.