The U.S. Copyright Office listing for Sonic the Hedgehog 2 includes a plot synopsis, potentially revealing how Knuckles will be introduced in the upcoming sequel. After the first movie proved to be a tremendous hit at the box office in early 2020, a Sonic the Hedgehog sequel was quickly ordered at Paramount Pictures. Not much has been revealed about the plot, but some fans have noticed some interesting details in the U.S. Copyright Office's listing for the movie.

Per the copyright listing, the "Description of Work" reads: "After settling in Green Hills, Sonic is ready for more freedom, and Tom and Maddie agree to leave him home while they go on vacation. But, no sooner are they gone, when Dr. Robotnik comes back, this time with a new partner, Knuckles, in search for an emerald that has the power to both build and destroy civilizations. Sonic teams up with his own sidekick, Tails, and together they embark on a journey to find the emerald before it falls into the wrong hands.

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This synopsis is plausible, given what we know about the Sonic the Hedgehog video game series. Knuckles is originally introduced as an antagonist, only to quickly end up becoming one of the most popular playable hero characters in the series. It seems like the movie Sonic the Hedgehog 2 will similarly introduce Knuckles as a threat to Sonic, but because the character is so popular with fans, it seems more than likely he'll become a hero by the end.

Because it hasn't been announced by Paramount Pictures, Knuckles' inclusion in Sonic the Hedgehog 2 isn't officially confirmed. At this point, however, the cat is pretty much out of the bag. A statue of the red echidna had previously been spotted on the set alongside statues of Sonic and Tails. There have also been reports of the character's inclusion with Aquaman and Game of Thrones star Jason Momoa eyed for the role.

What we do know is that screenwriters Pat Casey and Josh Miller have returned to write the script for Sonic the Hedgehog 2, and Jeff Fowler is also back in the director's chair. Ben Schwartz will again provide the voice of the titular hedgehog with Jim Carrey reprising the role of the villain Dr. Robotnik. James Marsden and Tika Sumpter also return as the Wachowskis and Colleen O'Shaughnessey reprises her role as Tails from the video game series to voice the double-tailed fox in Sonic the Hedgehog 2.

"That's a wrap in Vancouver! Thank you to all the amazing cast/crew in this city," Fowler posted to Twitter earlier this month, announcing that filming on the sequel had finished. "So much incredible talent helping make Sonic the Hedgehog 2 truly special (and spoiler alert... EPIC!)"

Given the success of the first movie and the anticipation for the sequel, it seems likely that many fans will turn out for Sonic the Hedgehog 2 when it is released next year. The movie is scheduled to premiere in theaters on April 8, 2022. The new details about the plot can be found at the official listing from the U.S. Copyright Office.