The casting director for Joker: Folie a Deux opened up about Lady Gaga‘s performance as Harley Quinn.

The 38-year-old actress and pop star is set to bring the iconic anti-hero to life alongside Joaquin Phoenix‘s version of the Joker in the musical movie.

During a recent appearance, casting director Francine Maisler reflected on Gaga and revealed that she was not the one to cast her in the project and added that the singer “surprised” her in a big way.

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“She’s so good in it, you guys,” Francine said, via Deadline. “She’s going to blow your mind. I didn’t suggest Lady Gaga. It wasn’t my idea. That was Todd Phillips, before me. But I will tell you, she’s really surprising — and really good. I saw it and I was really surprised.”

Francine continued, saying, “I mean, we all knew what she could do in A Star is Born, but I thought, ‘Oh, well, that’s kind of in her wheelhouse.’ Something she could do and just be real. But this… Man, she’s good. Joaquin blows your mind, but that she could keep up with him, and be real — and not just wiped off the screen by what that role is and what the performance is — shows she’s good.”

Joker: Folie a Deux arrives in theaters on October 4. Check out the teaser trailer.