Matt Damon and Casey Affleck Dish on Rob Gronkowski's Cameo in 'The Instigators' (Exclusive)

ET's Rachel Smith talks to 'The Instigators' stars on their upcoming action comedy flick, premiering on Apple TV+ Aug. 9.

More than 25 years after starring alongside one another in Good Will HuntingMatt Damon and Casey Affleck are once again sharing the screen in Apple TV+'s The Instigators.

The upcoming action comedy follows struggling father Rory (Damon) and ex-con Cobby (Affleck), two unlikely partners who team up to steal from a corrupt politician. The job goes wrong, though, and, as the duo is pursued by police, bureaucrats and crime bosses, they enlist the help of Rory's therapist (Hong Chau) to evade capture.

The Doug Liman-directed film also stars Michael Stuhlbarg, Paul Walter Hauser, Ving Rhames, Alfred Molina, and Toby Jones, with appearances from Jack Harlow, Ron Perlman and NFL legend Rob Gronkowski.

Damon and Affleck cannot help but gush about the former football player's appearance in the upcoming film, telling ET's Rachel Smith that Gronk was Affleck's first choice for his unnamed role. Unsurprisingly, the actors are big fans of the retired athlete who played nine seasons for their beloved New England Patriots.

Rob Gronkowski in Apple TV+'s 'The Instigators' - Apple TV+

"Devin Walsh, our producer called him up and, and got him here," Affleck, who co-wrote the film with Chuck MacLean, tells ET. "He really thought he was going to be in it more."

"He was only there for, you know, a certain amount of time," Affleck adds. "Everybody loves [Gronk]." 

Gronk was seemingly a perfect fit for the film comedy, which Damon shares that he signed up for in hopes of giving viewers something to watch that will have them laughing "the whole way through it."

"It's a lot of fun, that's what we try to do," Damon adds. "We wanted to make a really fun film and hopefully you laugh the whole way through it."

Affleck says Damon was also his first pick for the role of former Marine Rory.

"Whenever I'm writing something or trying to put something together, I think about Matt. He just says no to all of it! At a certain point you have to have backups in mind. If I sent it to his wife, Lucy, I get more likely to get a yes," he quips about Damon's longtime love, Luciana Bozán, who also serves as a producer on the action flick.

Matt Damon and Casey Affleck in 'The Instigators' - Apple TV+

The Instigators' Boston setting takes Damon and Affleck back to their old stomping grounds, which the actors admit was a welcome perk to working together again.

"We've been able to come back a few times for work; it started with Good Will Hunting and The Departed and Gone Baby Gone. It's really fun to come home and kind of fall into that because the whole culture, the whole kind of attitude... there's this kind of cynical sarcastic Boston thing that comes naturally to us, I think," Damon says, adding that this newest project also serves as a "love letter" to Boston.

Affleck notes that "it's hard not to come [to Boston] and not plan some scene in Fenway Park. The whole city feels like home."

The heist flick, which is filled with car chases and hostage situations, boasts a crucial theme that most viewers might not expect from a high-speed drama: the importance of mental health. 

Chau serves as a rare voice of reason in the comedy, although it proves mostly futile when Dr. Donna Rivera is "taken hostage" by Rory and Cobby amid their robbery gone awry.

Hong Chau, Casey Affleck and Matt Damon in 'The Instigators.' - Apple TV+

The onscreen dynamic echoed the cast's vibes behind the scenes, which Chau shares was like "being invited to the family barbecue."

"You get to be there and experience all the history and watch them gently rib each other. It was really fun," she said of working alongside Damon and Affleck.

And when it comes to her character's role in the misadvised adventure, Chau shares that Dr. Rivera's scenes with Rory give a "nice" balance to the film's comedic nature.

"I haven't been to therapy but I imagine that most [sessions] are more open and vulnerable than [some] marriages. So, I think with those scenes with Dr. Rivera and Rory [are] a very sensitive environment," she tells ET. "And then you juxtapose [them] with the car chases and everything else going on, [and it's] a really nice thing to balance and make it fit into this action movie."

While Rory and Cobby's relationship is markedly different from Damon and Affleck's -- who go way back, even living together in their early days in Hollywood -- playing their parts was a lot of fun for the actors. 

"It a good comedic setup for these guys who are kind of an odd couple in ways," Damon explains. "Casey's character really just wants to make friends [but] he doesn't ever come out and say that. And my character is just in this desperate situation and doesn't know what [he's] doing."

Damon aptly summarizes the film with one more thought: "If you can't get the A Team, B Team or C Team, you get us. That's how we thought about it."

The Instigators will premiere in select theaters Aug. 2. It will arrive on Apple TV+ Aug. 9.

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