According to insider reports, Paramount's “Transformers: The Last Knight” ties the franchise into Arthurian legend.

A recent development with the movie’s casting (via Mashable) falls consistently with the rumor: Liam Garrigan, who plays King Arthur in ABC’s “Once Upon a Time”, has been tapped to play the character -- of course, portraying a completely different take on the hero -- in the upcoming movie.

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Not much is known regarding the movie's plot, but rumors previously suggested that King Arthur and Merlin would appear in the movie -- and Santiago Cabrera has reportedly been cast as Merlin.  Michael Bay is returning to direct the film, from a screenplay by "Iron Man's" Art Marcum and Matt Holloway.

"Transformers: Age of Extinction" star Mark Wahlberg is also set to return, reprising his role as Cade Yeager. He stars alongside Josh Duhamel, Tyrese Gibson, Isabela Moner, Laura Haddock, Jerrod Carmichael, Gil Birmingham and Anthony Hopkins. Details as to which Transformers are going to appear in the movie are currently kept under wraps.

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It will be interesting to see how the new movie ties everything together with the franchise, which has a Bumblebee spinoff and a sixth "Transformers" installment down the pipeline in the next two years.

Paramount has slated "Transformers: The Last Knight" a June 23, 2017 release.