House of Gucci” doesn’t come out until Nov. 24, but one line of dialogue has already become iconic.

As soon as the first trailer was released in July, footage of Lady Gaga as Patrizia Gucci reciting “Father, Son and House of Gucci,” while making the sign of the cross, became an internet sensation.

It turns out the line was an ad-lib by Gaga. “I would do it in the trailer all the time,” she told me, slipping into an Italian accent, on Thursday night at the Los Angeles premiere of the film at the Academy Museum of Motion Pictures. “I was doing it in the trailer and then something about that scene when we were doing it felt right. We did it, and it’s a testament to Ridley Scott as a director because he uses the stuff. He uses the creativity. He uses the love.”

Screenwriter Roberto Bentivegna told me, “That was Gaga the ad-libber at work. It’s iconic. Amazing. There was so many great ad libs that didn’t make the cut. That was certainly a great one. They just had such a great time riffing. I think that some writers might feel like their words are precious and everything has to be respected, but for me it was joyful. It was like they’re feeling it. It’s like music. It’s like they’re jamming and the melody is taking them to this awesome improvisation. I was very flattered that they felt like doing that.”

Gaga said the hardest part of taking on the role of Patrizia was getting inside her head. “The most challenging part was playing a murderer,” she said. “But I will say that after a lot of research, I realized that she knows she made a big mistake. And it was a lot of trauma that drove her toward this huge mistake that I know she regrets. So when you go see ‘House of Gucci,’ you will not watch a movie about some sexy, gold-digging murderess, you will watch a real woman fall in love and fall apart.”

She added, “I can’t wait for people to go out into theaters and see this movie because it’s so fun. So fun. And it looks like it’s going to be really dramatic. It is but it’s dramatic and funny and comedic.”

When I described the film as “delicious,” Gaga agreed: “It’s yummy. Yum, yum, yum.”

Meanwhile, Gaga also reiterated her support of Britney Spears after recently celebrating the end of her conservatorship in an Instagram post. “I have loved @britneyspears her whole career,” Gaga write alongside a photo of the two pop stars together at a past American Music Awards. “I looked up to her, admired her strength — she empowered so many people and still does. I couldn’t be more happy for you today. You never deserved what happened.”

Gaga told me last night that she would love to work with Spears: “I love all of Britney’s works. I can’t just name one [favorite]. I mean, ‘Oops!…I Did It Again,” is of course one of my favorites.”