Eric McCormack’s Son Makes Acting Debut Alongside Dad in ‘The Hunting Party’ (Exclusive)

Eric McCormack isn’t just dad to his only son, Finnigan McCormack. Now he’s taking on the title of on-set mentor!

The Will & Grace alum guests alongside his 23-year-old son in Finn’s TV debut: The premiere episode of NBC’s The Hunting Party season 2, in which the father-son duo play the younger and older versions of fictional serial killer Ron Simms.

Eric didn’t necessarily foresee himself acting with Finn in this capacity — “certainly not the serial killer part” — but he did envision himself growing old with his son. And now they’re doing so on screen, as the same guy.

“I think parents always, they come at it from two different angles,” Eric, 62, tells PEOPLE ahead of the premiere on Jan. 8. “Some people are like, ‘God, I just wish he was six again.’ I loved him when he was 4 or 5 and 6, but I’ve always had this sort of hope that one day we could be grownups together.”

He adds, “I foresaw that one day I just wanted to hang with this guy. And I do.”

Eric, who welcomed Finn in 2002 with then-wife Janet Holden, stars in the episode as the grown-up version of Simms: An Austin, Texas-based serial killer known in the Hunting Party universe for killing multiple women by breaking into their homes, hiding under their beds and drugging them. Eric handles the role of the older Simms, while Finn plays the character in flashback scenes — including a jarring opening sequence of him in action.

“This is an entirely new experience for both of us,” Finn says of the joint role. “I mean, what’s weird is that we didn’t get to necessarily be in the same scene together, but we’re playing the same person, so we had to think about the character the same way and how A is going to land to B. That was really special to be able to bond on crafting the character.”

Eric adds, “I’ve actually fantasized about playing father and son in something one day, but the idea of playing the same person… we spent a couple of days in my hotel room, Finn’s hotel room, just talking about this guy that we’re sharing. How do we embrace this guy in the same way so that we’re coming at it from a believable perspective?”

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Finn’s background in acting includes a few projects he worked on in high school and college, including some plays his dad would attend. Eric would often “help me with all my lines and getting the part down to a science,” Finn shares.

While the younger McCormack had a few opportunities over the years to see his dad act on set (it gave him “the confidence to try it out for the first time,” he says), things were different on the set of The Hunting Party.

That’s where Finn picked up on a few tips from his father: “It’s really cool seeing you lock in to going from take and out of take, you’re charming, you’re fun, you’re having a good time, and then you can just snap right into place for where they need you,” he tells his dad. “Learning to switch between is cool. That was an experience.”

As an acting coach, Eric was “descriptive, deliberate” and “very assuring of my work,” Finn adds.

“Finn always wanted to be his own guy, and I think he wasn’t someone that just wanted to sit around and say, ‘Oh, you must be Eric’s son,'” Eric says. “So this was a new experience as an adult to show up and you’re not just Eric’s son, you’re sharing a character and you’re an actor in your own right.”

The father-son duo can be seen in action in the season 2 premiere of The Hunting Party, which arrives at 10 p.m. ET on NBC.