The American Hustle cast from left, Amy Adams, Bradley Cooper, Jeremy Rennder, Christian Bale and Jennifer Lawrence.
De Niro plays a mob boss and `Batman' Bale piles on the kilos and bad toupee for crime-drama-comedy.
Christian Bale, Bradley Cooper, Jennifer Lawrence and Amy Adams were standing around the set of director David O Russell's new movie American Hustle when Robert De Niro walked in.
It was De Niro's first day of filming.
The acting great, who plays a mob boss in the crime-drama-comedy, went around and shook his colleagues' hands.
He was already great friends with Cooper and Lawrence after the trio last year worked on Russell's Silver Linings Playbook and then spent months on the Hollywood awards' circuit picking up nominations and trophies for their performances.
"I said, 'Yes, that's Christian Bale'," Russell laughed.
"He just starts to stare and said, 'Wow, he looks so different. He looks so great'.
"Then I had to reintroduce him again."
It's no surprise De Niro couldn't recognise Bale, the Welsh-born actor who plays 1970s Bronx con man Irving Rosenfeld in American Hustle.
As well as the toupee, Bale put on 20kg via a doughnut, pizza and cheeseburger diet for the character, who is comfortable duping victims in small-time schemes but becomes concerned when he is recruited by the FBI to devise a sting operation involving a fake Arab sheik to catch corrupt politicians.
Bale has become a master of manipulating his weight. For 2004's The Machinist the actor lost 29kg on a diet of apples, chewing gum and cigarettes to play a deathly looking industrial worker who had not slept for a year.
Six months later he put on 45kg of muscle, with little fat, to play Batman in
He then lost the muscle for his Oscar-winning role as boxer-turned drug addict Dicky Eklund in Russell's 2010
The Fighter
.
All it took for Bale to become interested in playing Rosenfeld were a few photos of the man the con man is based on.
American Hustle is inspired by a real 1970s sting dubbed ABSCAM.The FBI worked with scammer Mel Weinberg to pull off the operation which involved a fake sheik and led to the convictions of six Congressmen, a New Jersey mayor and other local government officials.
"When I first saw the pictures of the real Mel Weinberg he was not who I expected at all," Bale said.
"I just saw such incredible possibilities of what we could achieve together with this incredible cast."
The other cast members also transformed for the film.
Cooper, who plays ambitious, but dim-witted, FBI agent Richie DiMaso had his hair curled and talks while chewing his tongue.
Adams plays con woman Sydney Prosser, who wears revealing Diane von Furstenburg dresses and talks with a fake English accent.
Lawrence is Rosenfeld's unstable, estranged Long Island wife Rosalyn, who has big hair, red acrylic nails and a love for leopard print. De Niro, as Miami mob boss Victor Tellegio, has a big bald patch. American Hustle is the third part of a three-film evolution for Russell, following The Fighter and Silver Linings Playbook.
He brought in Bale and Adams from The Fighter and Cooper, Lawrence and De Niro from Silver Linings Playbook.
"When I go after a picture I'm moved by the characters first and foremost and their world," he said.
"With The Fighter, people would say 'It's a boxing movie'."I never thought 'Oh, it's a boxing movie'.It was a character movie. The same thing with Silver Linings Playbook. People would say, 'It's a mental illness movie' or 'It's a romantic comedy'. My head would snap every time I heard it.To me it was a story about Jennifer Lawrence, Bradley Cooper, Robert De Niro and Jacki Weaver.
"I have come to see I adore characters who are reinventing themselves, are salt of the earth, who are dreamers, are in a predicament and there are things they love in the world. That is what makes me want to make a picture.
"You have honest heartbreak and honest dreaming and enchantment."
Movie preview What: American Hustle When: Opens at cinemas January 23