Maya Hawke and Sadie Sink Surprise Gaten Matarazzo at His First Performance of 'Dear Evan Hansen'

It was a Stranger Things reunion on Tuesday night, when Maya Hawke and Sadie Sink stopped by to see Dear Evan Hansen's newest star Gaten Matarazzo as he took the stage

Things got a bit strange at Broadway's Dear Evan Hansen Tuesday night.

Stranger Things stars Maya Hawke and Sadie Sink were in the audience of New York City's Music Box Theatre, to support their Netflix costar Gaten Matarazzo on his first performance in the Tony-winning best musical.

All three posed together for photos after the show, Matarazzo — who is playing Evan's best friend Jared Kleinman in the show — sitting on the stage while Hawke, 24, and Sink, 20, chatted with him from the audience (backstage visits on Broadway are still suspended due to ongoing COVID safety protocols).

If Matarazzo looked particularly gleeful it's because he had no clue Hawke and Sink were coming.

"They surprised him, which was super cute!" a source on the scene exclusively tells PEOPLE, adding that the two praised Matarazzo for his performance. "Maya and Sadie loved the show."

Natalie Powers/Dear Evan Hansen

They weren't the only ones who turned up on Tuesday as viewers of the hit Netflix show flooded the theater to cheer on Matarazzo. "Stranger Things fans turned up for Gaten's first performance," the insider adds. "He got huge entrance applause. And there were tons of fans outside at the stage door. It was mobbed!"

While Matarazzo did his best to greet them all, Hawke and Sink made their exit — and didn't need to travel to the Upside Down to do it, either. "Maya and Sadie walked out the stage door unnoticed and ran down 45th Street," the source jokes.

Natalie Powers/Dear Evan Hansen

Dear Evan Hansen marks the long-awaited return to the stage for Matarazzo. The 19-year-old actor — an advocate for cleidocranial dysplasia, a condition that affects the development of bones and teeth — made his Broadway debut at the age of 9 in Priscilla, Queen of the Desert. He went on to appear in Godspell in 2013 for a one-night-only performance and was last seen as Gavroche in the 2014 revival of Les Misérables, a role he also played on the 25th Anniversary North American tour.

"I'm so stoked," he said on Live with Kelly and Ryan in May. "I got the news a little while ago, which is so mean because I want to tell everyone in my entire life and I haven't been able to until now. Now I can, and I'm so excited!"

"Words could never express how truly honored I am to be a part of this company," he added, in a statement. "This show has taught me so much about myself and to be able to participate in any capacity, let alone on Broadway, makes me want to melt. I am ecstatic to be back on stage and eternally grateful for the opportunity."

Natalie Powers/Dear Evan Hansen

Dear Evan Hansen reopened its Broadway production in December 2020.

Written by the Tony-winning composing team of Benj Pasek and Justin Paul from a book by Steven Levenson, the show tells the story of an anxiety-plagued high school loner named Evan who's paralyzed by the hyper-connectivity of social media and forced to watch the world from the outside looking in.

Trying to improve his self-image, Evan writes himself a letter that is mistaken for a classmate's suicide note and rides that error to popularity. (The story is loosely based on an experience Pasek witnessed in high school).

Since first opening on Broadway in December 2016, the Stacey Mindich-produced show has become a sold-out smash, its message of mental health awareness, teenage isolation and the importance of inclusiveness resonating with audiences of all ages. The show won six Tonys, the Grammy for best musical theater album, and the Oliver for its London production.

The musical now has three productions running across the globe, with its Broadway, North American Tour and West End companies once again playing in tandem.

Zachary Noah Piser, who currently plays Evan on Broadway, is making history as the first Asian American actor to play the role full-time. The production also currently stars actress Jessica Phillips, who starred with Matarazzo in Priscilla a decade ago.

But sadly, Broadway performances won't be happening for long. Back in June, it was announced Dear Evan Hansen would be closing on Sept. 18.

At closing, the production will have played 1,678 regular performances and 21 preview performances. The milestone makes it one of Broadway's 50 longest-running shows of all time.

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Just last week, Ben Platt — who originated the role of Evan, won a Tony for his performance, and went on to play the part on-screen in the 2021 film adaptation — opened up about the closing news to PEOPLE.

"It had a beautiful, long run, and it was very of the moment — and now we're at a new moment and it's time for new pieces, but I think the legacy will live on and in the ways that it changed lives of a lot of young people and opened a lot of conversations," Platt, 28, said, "I just hope they have a beautiful last couple weeks."

For tickets, visit www.dearevanhansen.com.