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Thomas Mann is an actor on the cusp. Think of Miles Teller right before the release of “The Spectacular Now” or Michael B. Jordan before “Fruitvale Station.” Once “Me and Earl and the Dying Girl” hits theaters over the course of the next month, the 23-year-old actor is going to find himself busier than ever.

Of course, Mann”s mug may be familiar to many moviegoers. He starred in the hit comedy “Project X” ($102 million worldwide) and had supporting roles in “Hansel and Gretel: Witch Hunters” and “Beautiful Creatures.” “Earl,” which won both the Grand Jury and Audience Awards at the 2015 Sundance Film Festival, is on a completely different level.

Based on Jesse Andrews' novel, “Me and Earl” centers on Greg (Mann), a Pittsburgh area high school senior whose life takes a turn after his mom (Connie Britton) pushes him to hang out with a family friend and classmate, Rachel (Olivia Cooke), who is battling leukemia. She, unfortunately, is the “Dying Girl” in the film”s title. Over the course of the school year Greg and his best friend Earl (newcomer RJ Cyler) attempt to entertain her with some of their silly movie remakes such as “Senior Citizen Kane” and “2:48 PM Cowboy,” along with an occasional excursion to buy a firecracker popsicle or two.

The baby-faced Mann could easily play a teenager until he”s 30, but he”s honest enough to admit playing someone that young again wasn't ideal. It was the screenplay and director Alfonso Gomez-Rejon”s vision, however, which made him fight for the part.

“This role was so good and while the character is so immature it felt like the most mature role I'd ever taken on,” Mann says. “Now I feel like this is my quintessential high school movie and I can't go back.”

Mann actually met with Gomez-Rejon to chat about a part in the filmmaker”s first feature, “The Town That Dreaded Sundown.” While that didn”t come to pass, they stayed in touch and that kept him top of mind when Gomez-Rejon began casting “Me and Earl.” That”s rarely the most enjoyable part of the process for an actor and it certainly wasn”t for Mann.

“Olivia was actually cast first, which [made me] pissed off,” Mann recalls bluntly. “We were the first Greg and Rachel to read together. We got together and had dinner [the night before] to just talk about the script and break the ice and hope the next day would go much smoother. Fortunately, it helped us and we had this instant bond. We came in to read together and Alfonso loved what were doing and when we left the room [I thought], ‘This is amazing.””

And then the pitfalls of the creative process reared their ugly head. Mann had to wait two more months as the filmmakers auditioned Cooke with other male leads. He jokes, “It was like we were cheating on each other. We were both brought back for the final screen test. [It was] so embarrassing. Now she's reading with me and two other Gregs.”

Mann realizes now that Gomez-Rejon was considering other actors who, in theory, had more dramatic experience, but is honest when he says “it was pretty brutal.”

“It went on for a long time,” Mann says. “We were auditioning with 30 pages of scenes. It was pretty intense.”

Obviously, Mann got the part and all that work with Cooke during the audition process paid off as it effectively doubled as rehearsals. That gave everyone involved a head start before the 24-day shoot began and let the visually inventive Gomez-Rejon take more chances on set.

“There is a scene, which is my proudest moment that I've ever put on film, where it's one long take for six minutes,” Mann says. “It”s a dramatic scene between me and Rachel and it was the quickest scene we shot. Four Takes. We just laid it all out there. You don't want it to be too rehearsed or too polished or do too much for it. We didn't even know it was going to be one set-up.”

One aspect of the film that will no doubt charm many moviegoers are those movie spoofs we mentioned earlier (and, yes, the idea owes a bit to Michel Gondry”s “Be Kind Rewind”). It”s somewhat remarkable Gomez-Rejon and his production team were able to put so much detail into them in the context of a three-week shoot. Mann can”t remember if any spoofs didn”t make the cut, but many of them were significantly longer than what you”ll see on screen.

“The 'Conversation' spoof goes on for five minutes, but you just get glimpse of it on the computer screen,” he says. “We knocked five of them out in a row. We did those shots whenever we could get away for a second. It was a lot of material to finish in that amount of time.”

Mann, who has a number of indies in the can, will segue from promoting “Me and Earl” to starring alongside Dakota Fanning and Jenny Slate in the Charlize Theron-produced drama “Brain on Fire,” where he happily gets to portray someone in his mid-20s. In the meantime, he continues to be touched by the reaction he”s received from viewers at Q&As all across the country.

“People come up to you and they are genuinely moved by the film and they are telling you their stores and their personal loss,” Mann says. “People are really connecting to it in a really personal way. We just set out to make something that would speak to people and, hopefully, it would [be a movie] not only for young people, but something people of all ages could relate to.”

“Me and Earl and the Dying Girl” opens in Los Angeles, New York, Toronto, Chicago and Washington, D.C. on Friday.

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