It’s time for the next Brooklyn superfan to go from sideline supporter to supporting cast.

Sean Astin will guest-star on the April 25 installment of Brooklyn Nine-Nine, EW has learned exclusively.

Astin, whose credits include two very important “ings” — Lord of the Rings and Stranger Things — will pop up in an episode of NBC’s cop comedy that takes place in real time. In “Ticking Clocks,” Jake (Andy Samberg) and his fellow detectives attempt to track down an elusive hacker who is wreaking havoc on the servers in the Nine-Nine, and Astin plays a sergeant in the NYPD Cyber Operations Unit who aids the Nine-Nine in the case.

Astin, who recently guest-starred on The Big Bang Theory, was one of the celebrity fans who took to social media to advocate for a second chance in the wake of Brooklyn’s cancellation last May by Fox, which helped propel its near-immediate rescue by NBC. “Here’s the thing about Brooklyn 99 being cancelled, I don’t want it to be,” he tweeted at the time. “I love all of those people & they earned the right 2 have a final season victory lap where I could emotionally prepare. Don’t know them. Have nothing 2 do with the show. I’m just a fan who deserves better.”

Brooklyn Nine-Nine - Season 6
Credit: John P. Fleenor/NBC

Brooklyn Nine-Nine co-creator Dan Goor certainly sounds like a fan of the actor. “Working with Sean Astin has been a dream of mine since I saw first saw Rudy,” he tells EW. “I’m what you call an Astin-head. When he tweeted his support for Brooklyn Nine-Nine as a member of the Guardians of the 99, I was blown away. I’m so excited to have him on the show.” (You can get a preview of Sergeant Knox in the first-look photos above and below. Andre Braugher’s Holt doesn’t seem too impressed with the progress of the mission.)

Another one of those outspoken fans, who is named Lin-Manuel Miranda, appeared on Brooklyn earlier this season, playing the brother of Amy (Melissa Fumero). Asked back in May if he planned to convert these famous fans into guest stars, Goor told EW, “We’re huge fans of all of those actors. And we’d love to try to figure out ways to put them on our world.”

In other words: Mark Hamill, we’ve got our eye on you.

Brooklyn returns to the schedule this Thursday at 9 p.m. ET, when Jake and Amy protecting a hospital-bound witness (Julia Sweeney) who happens to have twisted bowels.

Brooklyn Nine-Nine - Season 6
Credit: John P. Fleenor/NBC

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Brooklyn Nine-Nine

A group of ragtag cops — led by Jake Peralta (Andy Samberg) — run the 99th precinct of the NYPD.

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