If there's anything you need to know about Fantastic Beasts star Ezra Miller, it is that he is a massive Harry Potter fan, with an encyclopedic knowledge of J.K. Rowling's Wizarding World that can rival any die-hard Potterhead. That's why he originally was very, very confused when he found out the surprise reveal involving his character Credence Barebone that happens at the end of The Crimes of Grindelwald.

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Unlike audiences, who had to find out Credence's real lineage when the second Fantastic Beasts movie hit theaters this past weekend, Miller found out that he is actually Albus Dumbledore's secret brother before Fantastic Beasts and Where to Find Them came out in 2016. The problem is he didn't get the full story behind the reveal when he found out what it was, leaving him scratching his head for weeks.Miller told IGN the story of how he found out he actually is playing Aurelius Dumbledore, the lost brother of Albus Dumbledore, while doing press for the new movie. (You can watch Miller hilariously recount this tale in the video above.) It turns out Miller found out this twist almost two years ago while he was in Toronto, Canada on a press tour for Fantastic Beasts 1. At the time, he was on the bus traveling between events when producer David Heyman leaned over and said, "I'm going to tell you who you are.""I go, 'No way,'" Miller recalled. "[Heyman said,] 'You're Dumbledore's brother.' And I went, 'Aberforth?' And he went, 'Uhh, yeah.'"Instead of realizing he was playing a Dumbledore that the outside world doesn't yet know about, Miller misunderstood and thought he was playing a younger version of the known brother of Albus, aka Hog's Head Pub owner Aberforth Dumbledore. Because Miller is such a big fan, this seemingly exciting reveal left him puzzled instead, and he immediately thought of a string of questions."I'm like, 'Wait a second, David, how do I get an English accent? How do my eyes turn blue? This doesn't make any sense.' And he's like, 'That's all I know, that's all I can tell you for now,'" Miller shared. "Essentially, I thought I was Aberforth Dumbledore, the known brother of Dumbledore, and David -- we were on the loud bus. It was a miscommunication."It was J.K. Rowling herself, the mistress of all things Potter, who had to set Miller straight when they saw each other at a different event several weeks later."I see Jo, and I'm like, 'Jo, Jo, Jo. How do I acquire the English accent? How does it make any sense? We know where Aberforth was from the time that he was born.' And Jo said, 'Did David Heyman tell you this?' And I was like, 'Yeah,'" Miller said. "She was like, 'Oh, no. You're not Aberforth; you're Aurelius.' And I was like, 'Who's that?' And she's like, 'Nobody knows about him but me, darling, and you now.'"That's a secret Miller and the rest of the cast had to sit on for almost two years, but hopefully he knows more about the twist than those of us who saw it in theaters do. All the Crimes of Grindelwald ending had to offer fans was the tease that Grindelwald had won Credence over to his side. It's Grindelwald who revealed the news to the orphan that Credence actually was a secret brother of Albus named Aurelius. As for what that means for the future or how the timeline even adds up to this new revelation, audiences will have to wait until Fantastic Beasts 3 comes out on November 20, 2020.What do you make of Fantastic Beasts: The Crimes of Grindelwald's ending? Let us know in the comments!

Terri Schwartz is Editorial Manager of Entertainment at IGN. Talk to her on Twitter at @Terri_Schwartz