'Transformers One' Trailer: Chris Hemsworth Voices Young Optimus Prime in the Epic Origin Story

Transformers fans are getting a blast from the past in the franchise's upcoming origin story, Transformers One.

The first trailer for the upcoming film, directed by Josh Cooley, was released on Thursday, giving a first look at Chris Hemsworth voicing Orion Pax, a young Optimus Prime, alongside Brian Tyree Henry, who voices D-16, a young Megatron. And in true Cybertronian flair, the trailer was dropped in space! A live-streamed countdown showed fans the craft's journey into space and, after one hour, the craft reached its peak at 125,000 feet above the Earth, revealing the trailer with a custom introduction video from Hemsworth and Henry.

The trailer shows the two friends who start out as worker bots, unable to transform into anything. But, after they gain the ability to change into vehicles and gain weapons, they're tasked with a mission against an enemy threatening the Transformers' home planet of Cybertron. And as the battle against a mysterious, plant-like villain unfolds, loyalties are tested and friendships are unraveled.

Watch the full Transformers One trailer below.

ET spoke with Hemsworth and Henry at CinemaCon earlier this month, and they opened up about signing on to the Transformers franchise's first animated film in nearly four decades.

"The big appeal to both of us, being fans of this universe, is the opportunity to tell a different story," Hemsworth shared.

"We historically know them [as] mortal enemies, but here, they start off as friends. It's a great connection and bond, and they're two individuals who have something to prove," he explained. "Then the evolution into the characters that we either love or hate is an interesting sort of journey, but there's a lot of heart in the film, a lot of comedic elements. So it was a big adventure."

"Yeah, me and Chris figured out the best way to bring the realness to it was to live together for the first three months of the film," Henry joked. "Just to do a lot of vocal exercises. We even tried to do some of our own choreography which made it into the movie."

The star-studded voice cast also includes a mini Avengers reunion -- as Scarlett Johansson voices Elita-1 -- as well as Steve Buscemi, Laurence Fishburne, Keegan-Michael Key and Jon Hamm.

According to Paramount, the film is "the long-awaited origin story of how the most iconic characters in the Transformers universe, Orion Pax and D-16, went from brothers-in-arms to become sworn enemies, Optimus Prime and Megatron."

"It was nice to have the opportunity to come at it again and again and have it be orchestrated with Josh [at] the helm," Hemsworth shared. "It's different to a film experience where you kind of get one shot."

"I really joined this knowing that Chris was going to be my Optimus Prime and you just kind of play in that way 'cause you can feel the essence of who they are and then you sometimes get a chance to see what they do and you go, 'Oh I need to do this completely different,'" Henry told ET. "It truly is [us] living out our imaginary selves when we were like 10, 11, watching these things on Saturday morning. These characters are iconic to me and it's just a great adventure, especially to do it with this guy. It's wonderful."

Transformers One rolls out to theaters on Sept. 20.

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