Earlier this week, we reported that Once Upon a Time star Liam Garrigan signed on to play King Arthur in Paramount's upcoming action sequel Transformers: The Last Knight. This essentially confirmed months of rumors that this sequel will have connections to the medieval story involving both King Arthur and the mystical legend Merlin. Today, we have new details that may reveal the inspiration for this tale. While this report hasn't been confirmed, it's possible this tale was actually pilfered from the original Transformers animated series.

Before Liam Garrigan was cast, who ironically played King Arthur on Once Upon a Time, there had been plot rumors that the story centers on Optimus Prime returning to Earth in search of a mysterious artifact, which has ties to both King Arthur and the magician Merlin. Santiago Cabrera, who had previously been cast but whose character was never revealed, is playing Merlin.The Hollywood Reporter revisits the first time Transformers and King Arthur crossed paths, which may be the inspiration for this new tale.

Back in 1985, the Transformers animated series aired an episode entitled Decepticon Raider in King Arthur's Court. The episode featured a number of Autobots and Decepticons in present day who enter a cave that turns out to be a portal to 6th Century England, where they meet a re-named King Arthur (Sir Aetheling), his knights of the Round Table, and Merlin, who was called Beorht in this episode. The robots in disguise teamed up with Arthur to fend off the Decepticons and Mordred, re-named Sir Wigend, with jousting dragons, before the Transformers went back to their era.

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There was another medieval Transformers story told through the British Transformers comic book, which also came out in 1985. That story, a four-part tale, featured a lone Transformer wandering around 11th Century England, which is long after the King Arthur tale took place, but it's when his legend started to grow. Paramount has yet to confirm if this Transformers episode and comic book serve as the inspiration for this story, but it's worth noting that the massive writers room formed to generate sequel and spinoff ideas, was tasked with going back through the entire history of this franchise, including the original series, toys and comic books, to find ideas for sequels and spinoffs.

Another hint that this story may be based on the original animated series episode is the new poster revealed earlier this month, which showcased Optimus Prime's new look, but also featured a number of robot dragons in the background. Transformers 5 was written by Art Marcum, Matt Holloway and Ken Nolan, who were all part of the writers room, but Paramount hasn't offered any official story details yet. It's also worth noting that set photos recently surfaced featured actors wearing medieval costumes while riding on horseback, but we still don't know how they fit into the story quite yet. Here are two clips from the animated series episode 'A Decepticon Raider in King Arthur's Court'.