Ezra Miller is stoked about playing the Flash. How could he not be? The indie-fabulous Perks of Being a Wallflower star has already expanded his presence on the global stage with a key role in Fantastic Beasts and Where to Find Them, and his superspeedster Barry Allen had brief cameos last year in Batman v Superman and Suicide Squad. But that’s all mere prelude to Justice League, which prominently features the young hero alongside Batman, Wonder Woman, Aquaman, Cyborg, and…perhaps some other superpowered denizens of the DC universe.

“I was definitely nervous and excited every single day,” Miller says about being on set. (EW spoke with the actor in June.) “I definitely was feeling like Barry, stepping into the big leagues with this incredible group of collaborators. Feeling like Barry, trying to do the best job I could do. I think that does sum up Barry in this movie, whether you’re talking about his social interactions or his attempts to harness his powers and be a superhero. It’s nice when you have that ‘art mirror life mirror art mirror life mirror art’ thing going on.”

Every superhero needs a costume, of course, and the bigscreen Flash sports a particularly elaborate riff on the character’s iconic lightning-red ensemble. Putting on the costume was, initially, a lengthy expedition. “There was a time towards the beginning where it was a very long, delicate process, where everyone was afraid of everything breaking,” Miller laughs. “I would feel like a Victorian lady with my chambermaids. Sometimes I would ask them if they could brush my hair and ask me about the boys whom I fancied.”

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By the end of shooting, the costuming process was a bit less intense. But all this talk about the Flash outfit leads, inevitably, to an important bit of Flash lore: The fact that, in his original Silver Age incarnation, Barry Allen got into his costume via a spring-loaded ring contraption.

“Well, you know, look,” says Miller. “I can confirm, spoiler alert, his suit does not pop out of his ring [in the movie].” Miller, who speaks with fluency about the different eras of Flash lore, has clearly anticipated this question. “Things have to progress, you know? Original Barry Allen was clearly an incredibly, incredibly clever scientist. We acknowledge and respect that.” He adds, playfully, “We want to apologize to the fans who are mad about the ring thing.”