Lady Gaga on How She Improvised One of 'House of Gucci's Best Lines (Exclusive)

ET spoke to the cast about some of the film's most iconic moments, staying in character and working with the legendary Al Pacino.

Lady Gaga has us all reciting a prayer to the Gucci gods. ET's Lauren Zima talked to the House of Gucci cast about how one of the film's most memorable lines came to be.

"That was something Jared [Leto] and I came up with together," Gaga, who stars as Italian socialite Patrizia Reggiani, who went to prison for hiring a hitman to kill her ex-husband, Maurizio Gucci, said of the now-viral prayer.

When asked if the line was always part of the script, the 35-year-old pop star revealed that the spontaneous one-liner was improvised, but it quickly stuck after giving it a go the first time around.

"Father, son and house of Gucci? Well, it was the first time, and then we kept it." Gaga revealed. "It was not in the script," Jared Leto, who plays Gucci businessman and fashion designer Paolo Gucci, confirmed.

"These things came to us, I think they came from a real place of spontaneity on set, where you can do as much work as possible before, and then when you get there, you just throw it out, and you just talk to each other," the "Stupid Love" singer added.

The cast got deep into character for the film, so much so that they almost forgot their real-life identities. Adam Driver, who plays Maurizio Gucci in the movie, said it wasn't until he left the set that he realized he wasn't actually the Italian fashion-house head that he was portraying onscreen.

"I kept a pair of Gucci shoes, but I always found this, where you are playing a character for three or four months, I start feeling like, 'This is who I am,' and then you take the clothes home, and you try to wear them in life and I'm like, 'I am not this person at all,'" Driver explained.

Getting lost in these characters is something Gaga has been open about, previously telling British Vogue that the role took a real toll on her.

"Just to echo what Adam said, I really got lost in that character," Gaga shared. "I got lost living, because we also shot in Italy, so whether you were on set, or you were in the world, it all kind of looked the same, except there was cameras, and I try not to focus on where the cameras are when we are working, so there was a real blending of the world."

For Salma Hayek, who plays the part of Gaga's sidekick, it took seeing and hearing Gaga speak in an American accent to realize she wasn't actually the one-time Gucci heiress.

"I heard her yesterday, and I was like, 'Oh, she sounds so American,' because I was so confused for the whole time we were there, even on the phone before we started, I only heard Patrizia, so it was weird. It was shocking to me," she said.

When it comes to breaking away from their characters and getting back to reality, both Driver and Gaga said they try to do so as soon as possible.

"I find I never have a problem leaving it," Driver revealed. "I always want it to be over."

"I also tend to really desire to drop my character as quickly as possible. This time I didn't do the things I normally do, like dye my hair. I did drop my accent, right away, but I think the hardest thing for me, was psychologically to drop the character," Gaga added. "When you start to frame your life and the way you see the world around money, where things have value, like, who matters to me, what person is going to provide for me what I need in order to make this happen, that framework of seeing the world in that way, that's not who I really am, that's who she is. For what it's worth, I don't know entirely what my process is like to get rid of a character. I do know that when I went home, a lot of people in my life told told me that I had no accent, but was acting weird."

While Gaga admitted that it did take a while to drop her House of Gucci character, she's not sure if Patrizia will ever fully leave her.

"Patrizia's weird. To me, she's a weird bird. She doesn't really fit in," Gaga went on to say. "She's got this kind of strange sexual energy where she's really trying to get what she wants all the time, so I tried to drop it, and I tried to drop it as fast as I could, but I don't know if she's ever fully left me."

The star-studded ensemble cast also includes the legendary Al Pacino, who stars as Aldo Gucci, the eldest son of Guccio Gucci, who founded the famous company. While each member of the cast carries their own star power, they all couldn't help but rave about Pacino, with Leto calling the award-winning actor "one of the greatest actors to ever be on screen."

"I'm just sitting here thinking about how Pacino, who we have to say out loud, is one of the greatest actors to ever be on screen. And, this is a person who's taught us all how it should be, what it can be," Leto said of the screen legend. "To teach us to reach as high as we can, to fail often, and a person who really changed my life."

See this iconic group of actors tell the story of this tumultuous time in the Gucci family's history, when House of Gucci hits theaters Nov. 24.

And, tune in to Wednesday's episode of Entertainment Tonight for more of ET's interview with the cast of House of Gucci.

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