"Obviously there's a special significance for portraying Catwoman," the Glee alum said, before footage played that showed her recording her lines and viewers were given a preview of the film, which was released Tuesday.
Rivera joins a long line of women who have portrayed Catwoman, a.k.a Selina Kyle, onscreen - including Eartha Kitt, Julie Newmar, Michelle Pfeiffer, Halle Berry and Anne Hathaway in live action, and Zoë Kravitz, Jennifer Morrison and Eliza Dushku in voice roles.
"Every actress that I've ever loved has played Catwoman in some shape or form," Rivera told ET. "And I'm honored I get to play [her] for this movie."
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Naya Rivera (L); Catwoman
Naya Rivera recording her lines as Catwoman
The movie sees Batman on track to solving a string of murders in Gotham City. As his path crosses with Catwoman's, he can be heard asking, "Why are you running?" Rivera's character replies, "You could use a little fun."
The voice cast of the film also includes Josh Duhamel as Harvey Dent, Billy Burke as James Gordon, David Dastmalchian as Calendar Man, Troy Baker as the Joker, Jack Quaid as Alberto, Amy Landecker as Barbara Gordon and Titus Welliver as Carmine Falcone.
This will mark Rivera's last project, as she wasn't in production on any other titles before her death. The actress died in July 2020 as a result of a drowning accident after she and her son Josey, now 5, rented a boat at Lake Piru in Southern California.
Jon Kopaloff/FilmMagic Naya Rivera
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Josey, who was 4 at the time, had been found asleep on the boat as it drifted on the waters of Lake Piru after his mother failed to return it. And Rivera - who rose to fame playing the outspoken, gay cheerleader Santana Lopez on Fox's musical comedy series Glee - was missing.
The 33-year-old actress' body was discovered floating in a remote section of the lake five days later by Ventura County search and rescue divers.
Rivera drowned after exhausting herself while struggling to get Josey back into the boat after the two went swimming, according to a report released by the Ventura County Medical Examiner.
"It's still pretty much a big blur of pain almost a year later," the star's father, George Rivera, told PEOPLE earlier this month, fighting back tears. "Things are slowly coming a little more into focus, but I don't know if I'll ever find closure from this. I miss her every day."
The Long Halloween is a two-part film, with the first part available now on digital and Blu-ray.