North Shore native Alex Moffat didn’t have to hear Eric Trump speak — or even watch him move — to know how to play the presidential son on “Saturday Night Live.”

In a photo that Donald Trump Jr. (right) posted on Instagram in September 2016, he poses with sister Ivanka and brother Eric.

Once assigned the role, Moffat zeroed in on a still photo, the infamous image Donald Trump Jr. posted on Instagram before last year’s election, hashtagged #millennialsfortrump, that showed Eric with a pained expression, lurking behind his tight-lipped, eerily staring siblings.

“It looked like Eric popped into the picture unbeknownst to Ivanka and Donald Jr.,” Moffat said. “Just the look on his face — I went from there.”

His depiction of the first son as an ill-at-ease imbecile who blurts “I’m Eric!” gave Moffat abundant exposure during his first season on the NBC late-night stalwart. Eric’s name, he said, “is the only thing that someone has yelled at me on the street.”

But he’s done much more since joining the show last October. He’s impersonated Joe Scarborough, Al Franken, Anderson Cooper and Casey Affleck; played a Bethlehem wise man and a hamster, and enjoyed a solo moment on Weekend Update as a glib guy who just bought a boat.

Alex Moffat plays the Guy Who Just Bought a Boat alongside Colin Jost on “Saturday Night Live.” | NBC

As of late July he was awaiting word on whether he’ll be back for the new “SNL” season this fall — never a sure thing, especially for a freshman cast member. If all goes well, he could be back on the air as soon as the prime-time “Weekend Update: Summer Edition” episodes premiere Aug. 10.

And not a minute too soon, with White House controversies taking no summer break. Moffat’s Eric Trump is always seen at the side of Donald Jr. (Mikey Day), and when everyone’s talking about a scandal like Donald Jr.’s meeting with Russians, Moffat said, being off the air is “a bummer because it would be great to have a show as an outlet to comment on everything.”

Since the 42nd season wrapped in May, Moffat has been performing stand-up dates and talked to the Sun-Times the day after hosting a promotional event for John Dewar & Sons at the Dawson on West Grand. It was a homecoming for the actor, who grew up in several towns including Wilmette, Winnetka, Glencoe and Kenilworth. “We made the rounds,” he said.

Alex Moffat hosts a July 13, 2017, event for John Dewar & Sons at the Dawson in Chicago. | Provided photo

He dabbled in performing as a kid, training at the Piven Theatre Workshop in Evanston and acting in school and community theater. After college he got serious about getting funny, taking Second City and iO classes.

His one-man show “Good Little Winnetka Boy” ran in 2010 at the Annoyance, where he also understudied “Coed Prison Sluts,” the company’s long-running exercise in bad taste set to music. “That was a pretty good deal for me,” Moffat said. “Kind of a nice badge of honor.”

At iO Moffat hosted “The El Show,” an onstage talk show. “It was late,” he said, “and there weren’t always a ton of people there, so we kinda had free rein to experiment.” He also improvised on a Second City cruise ship troupe alongside future “SNL” player Cecily Strong, who would be a great help later when Moffat got hired at the show as well.

He had relocated to Los Angeles when “SNL” came to check out prospective talent at a special iO showcase in Chicago — just as Moffat was back home visiting family.

“I was sitting in my agent’s office here in Chicago – Marisa Paonessa, who’s the best — and she said, ‘You know, ‘SNL’s’ coming to town next week. Want me to see if we can get you up there?’ ”

Even a president’s boneheaded son knows the answer to that.

Alex Moffat plays MSNBC host Joe Scarborough, with Kate McKinnon as Mika Brzezinski, on “Saturday Night Live” on May 6, 2017. | NBC