Yellowstone star Cole Hauser turned to social media to wish his old friend Ben Affleck a happy birthday, and he inadvertently stunned his followers when he shared a throwback picture from a film many fans had no idea he was in.

Affleck turned 49 on Aug. 15, and Hauser subsequently posted a black-and-white throwback photo to Instagram that shows himself, Affleck and Matt Damon all together with some of the rest of the cast of Good Will Hunting, which launched both Affleck and Damon into superstardom when it won Best Original Screenplay at the Academy Awards in 1997.

"Happy belated bday brotha @benaffleck much love!" Hauser writes, adding the hashtag #goodwillhunting.

Hauser played the role of Billy McBride in the film, and he also appeared with Affleck and Damon in School Ties and Affleck again in Dazed and Confused. The actor has red hair in real life, and even now, he bears only a small resemblance to his Yellowstone character of Rip Wheeler, the gruff foreman of the Dutton ranch who has a very dark backstory. He's virtually unrecognizable in the older picture, and that led fans to react with amazement as they connected the dots and realized they'd seen the actor before and not known it.

Hauser dyes his hair as part of his preparation for his Yellowstone role. His character, Rip, has had a tempestuous on-again, off-again romance with Beth Dutton (Kelly Reilly) for years, and as he explained during an appearance on the Jenny McCarthy Show, the two actors bear too strong a resemblance to one another in real life, necessitating the change.

"When I first got the role, as you know Kelly's a ginger and I'm ginger as well. So we looked like we were brother and sister" he told McCarthy with a laugh. "So we kind of had to make sure that wouldn't be the case."

Yellowstone Season 4 will air on the Paramount Network and Paramount+ beginning on Nov. 7.  Subscribe to the streaming service to make sure you don't miss out.

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