Alfonso Cuarón admits that he was an odd choice to direct the third Harry Potter movie.

In a new interview with Total Film commemorating the 20th anniversary of Harry Potter and the Prisoner of Azkaban, the Children of Men filmmaker said he was as surprised as anyone when he was offered directorial reins for the wizard sequel, as he’d just come off of his seminal erotic road-trip masterpiece Y Tu Mamá También. "I was confused because it was completely not on my radar," Cuarón said of the Potter series.

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The Roma filmmaker said he changed his mind after discussing the project with a friend. "I speak often with Guillermo [del Toro], and a couple of days after, I said, 'You know, they offered me this Harry Potter film, but it’s really weird they offer me this,’” Cuarón recalled. “He said, 'Wait, wait, wait, you said you haven’t read Harry Potter?' I said, 'I don’t think it’s for me.' In very florid lexicon, in Spanish, he said, 'You are an arrogant a--hole.'"

After Home Alone director Chris Columbus brought a family-friendly sense of wonder and whimsy to the first two Potter films — Sorcerer’s Stone and Chamber of Secrets — Warner Bros. opted to shake things up by hiring a new filmmaker with different sensibilities. Cuarón had previously adapted other pieces of popular literature, including Charles Dickens’ Great Expectations and Frances Hodgson Burnett’s A Little Princess, and he brought a wildly different tone to the third Hogwarts adventure.

Harry Potter producer David Heyman explained the decision to hire Cuarón. "I’d seen Y Tu Mamá También, which I loved, and I oddly thought he’d be the perfect director for the third Potter," he said. "That’s not what some might think. Can you imagine what some thought Harry, Ron and Hermione would get up to, having seen Y Tu Mamá También?... Y Tu Mamá was about the last moments of being a teenager, and Azkaban was about the first moments of being a teenager… I felt he could make the show feel, in a way, more contemporary. And just bring his cinematic wizardry.”

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Indeed, Cuarón’s Prisoner of Azkaban marks an invigorating departure from the style of the preceding two movies — it employs a color palette with greater emphasis on grays and blues, and swaps the students’ formal robes for casualwear that makes them feel more like everyday teenagers. The constantly-roaming camerawork that later breathed incredible energy into movies like Children of Men and Gravity brings a strong sense of urgency to Azkaban, and the thematic focus on Harry’s blossoming self-reliance makes for a thoughtful, intimate coming-of-age story that really reckons with its characters growing up.

Harry Potter and the Prisoner of Azkaban premiered in New York City 20 years ago today. Read Total Film's interview excerpt with Cuarón here.