(Photo Credit: Code Black Films/YouTube)

The elegant and classy Jennifer Hudson seen walking the red carpet at various events is nowhere to be found in her new movie "The Inevitable Defeat of Mister and Pete."

The Oscar-winning actress, 32, plays Gloria, a heroin addict, who is eventually taken away from her son for dealing and using drugs.

Tattoos, skimpy outfits, crazy hair and sexual exploits are a few elements that come with the character. "They [even] wanted me to lose a little bit more weight for the role," said Hudson, who lost 80 pounds in 2010 while being the spokeswoman for Weight Watchers.

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Hudson, adding that a heroin addict doesn't have to look sickly thin, ended up filming at her normal weight, but told ABC News that her transformation still took multiple days each time before filming.

"That was like a two, three day process, especially with the tattoos," she told ABC. "I remember them testing them out and putting them on me right before filming and it was like days before filming."

Hudson said in the middle of the process if she wanted to go out in public, she would have to wrap up "from head to toe," so not to spoil the surprise or even scare her son.

"It would creep him out and would scare him," she said of her new physical appearance. "So, to snap [him] out of it and be like, 'No, mommy's here, I'm back.'"

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The actress said her son David Jr., 4, who she had in 2009 with fiance David Otunga, was also the rock she needed to make her smile after a hard day of filming some dark content.

"My son being there to see it asking, 'Mommy, why are you acting like that?' So, just trying to be a good mommy versus a bad one [like her character]," she said. "That kind of brought me back to reality."

While most know her as Jennifer Hudson, the singer/actress who rose to fame on "American Idol" in 2004, she said David Jr. sees her very differently.

"The only time I'm Jennifer Hudson is when he's saying my name," she said. "Other than that, if it's on television, commercials, a movie, anything - that's mommy."

"The Inevitable Defeat of Mister and Pete" hits theaters on Oct. 11.