Alan Ruck has acted in more than 100 movies and TV shows, but the odds are you know him from one of two things: “Ferris Bueller's Day Off,” where he played Bueller's best friend, Cameron Frye; or “Succession,” where he played Connor Roy, the odd sibling out in an uber-wealthy family vying for power.

His first major work still has staying power 38 years later: On Sunday, Ruck will be at the Emerson Colonial Theater for a screening of “Ferris Bueller” followed by a Q&A.

“I knew that it was a really good part,” Ruck told GBH’s Morning Edition co-host Jeremy Siegel. “He's the character that has the problem. He's the one that has the dramatic challenge. So I knew it was really great part and I worked hard on it, but I had no idea that it was going to be anything more than just kind of a happy teen comedy.”

Ruck was in his 20s when he played Cameron, the carefree protagonist’s best friend who seems to be dealing with depression, though that’s never explicitly named in the film.

In one scene, Cameron is laying in bed in his messy room, staring into the ceiling and singing mournfully to himself.

“John Hughes — in that scene where I was lying in bed and Ferris keeps calling me — he said, ‘I want you to sing a funeral dirge for yourself,’” Ruck said. “And I didn't know any funeral dirges, but my father had a record of Paul Robeson singing spirituals that we'd listened to over and over again.”

He started to sing that song, he said, when Hughes recommended a lyric change: “Let my Cameron go.”

“That's where that came from, was me and Hughes kind of coming up with that together,” Ruck said.

The more recent role for which Ruck is best known, as Connor Roy in “Succession,” almost didn’t happen, he said.

He was back home in Los Angeles on a break from filming a TV version of “The Exorcist” in Chicago, he said. On his brief trip back to Los Angeles, he said, he was supposed to audition for “Succession.”

In his absence, his wife, actor Mireille Enos, had taken on extra caregiving responsibilities for their young children. And the day of the audition, Enos had asked him to come spend time with her and their son Larkin.

“My wife said to me, on Monday morning, ‘Before you go back, I want you to take Larkin, our little boy, to this mommy and me music class. I want you to come with us,’” he recalled.

Ruck said he told his wife couldn’t come. He had an audition for an HBO show, he said.

“And she starts weeping because she was really stressed out,” he said.

He called his manager and said he wouldn’t be able to make the audition after all, he said. Ruck went to his son’s music class, left his phone outside, and came back to messages asking him to stop by “Succession” executive producer Adam McKay’s house before he left town again.

“I went to Adam McKay's house, and I really didn't know the material,” Ruck said. “And Adam said, ‘You know the situation.’ And I said, ‘yeah.’ He said, ‘Make it up, whatever comes out of your mouth.’ We just started kind of improving.”

When he landed in Chicago, he got another call: He had the part.

“It was one of those things where it was just — it fell out of the sky and fell into my lap. Left to my own devices, I will always screw things up,” he said.

Ruck’s “Succession” character also has a tendency to screw things up. But while Ruck said there’s a piece of him in every character he plays, he’s not sure he welcomes the comparison.

“Kieran Culkin said, actually, ‘I don't think they knew who Connor was until you showed up,’” Ruck said. “And he said, ‘I think basically Connor is you.’ He said it with love, but I wasn't sure I appreciated that.”