You might assume a “Stranger Things” star would take full advantage of a visit to the Science Museum of Minnesota by stocking up on those brontosaurus-boasting sweatshirts that became all the rage after making cameos in the beloved Netflix series.

But David Harbour, who plays Chief of Police Jim Hopper, couldn’t bother popping into the gift shop. He was too busy pining for a piece of State Fair seed art that got away.

A little over a decade ago, Harbour was visiting the Great Minnesota Get-Together with his ex-fiancée, who grew up in Apple Valley, when a stunning portrait of actor Tom Selleck caught his eye. The pièce de résistance: The actor’s name was spelled S-E-L-L-A-C-K.

Harbour had to have it. He haggled with the artist, offering up to $1,000, but she finally decided she couldn’t part with it.

“You would think that if it was that personal, she would have gotten the name right,” Harbour said at the museum last week, wrapping up a flurry of publicity stops that included the Twin Cities Pride parade and a costume contest at the Mall of America.

In a weird coincidence, the third season of “Stranger,” premiering Thursday, opens with Harbour’s character watching an episode of the Selleck series “Magnum P.I.” He’s heavier and paler than when we last left him, trading in his pill addiction for a steady diet of Schlitz beer and Tostitos.

The only crisis capable of stirring Hopper from couch-potato mode is evidence that his adopted daughter, Eleven (Millie Bobby Brown), and her new boyfriend Mike (Finn Wolfhard) are doing more than playing board games in her bedroom.

“He’s in full dad mode in a certain way. He’s clearly eating his feelings,” said Harbour.

During the break after Season 2, which came out nearly two years ago, the actor bulked up for a starring role in this spring’s film reboot of “Hellboy.” But for his return to “Stranger Things,” he simply stopped working out and started ordering extra muffins.

“As a person with pride and vanity, I had mixed feelings about it,” he said. “But for the character, it’s great.”

Hopper has more to worry about than his waistline.

The third season takes place in the summer of 1985, roughly a year after our plucky heroes of Hawkins, Ind., sealed the Mind Flayer beneath the Earth. Now the monster is determined to seep back to the surface, a goal made all the more likely when pesky Russians unlock the Gate to the Upside Down.

Before you can ask “Where’s the beef?” Hopper is forced once again to become an action hero.

One of the kids nicknames him Fat Rambo.

“I love that line!” said Harbour, pecking at a small salad and stroking a long beard that suggests he got back into shape by chopping down trees next to Babe the Blue Ox.

The reference to Sly Stallone’s character isn’t the only callback to the ’80s. The show continues to celebrate the decade’s much maligned music with a soundtrack that may give you a new appreciation for Corey Hart’s “No Surrender” and REO Speedwagon’s “Can’t Fight This Feeling.” (First Avenue in Minneapolis is throwing a “Stranger Things” dance party Friday, hosted by DJ Jake Rudh.)

“Princess Bride” hunk Cary Elwes plays a corrupt hero, a clever bit of casting that follows invitations to “Goonies” good guy Sean Astin and “Aliens” sleazeball Paul Reiser to last season’s party.

Characters veg out to episodes of “Cheers” and “Miami Vice.” Ralph Macchio is the Sexiest Man Alive. Lucas (Caleb McLaughlin) defends the taste of New Coke, a product shelved the year after the teen actor was born. (Coca-Cola is reintroducing the brand this summer to take advantage of the anticipated curiosity.)

“In the first season, the biggest thing was the wall telephone with the long cord. I remember all the kids going, ‘What’s that?’ ” said Harbour, who at 44 is old enough to remember pulling the receiver into his bedroom when he was their age so he could chat privately with girls.

If the series winked at beloved movies in the past, the new episodes are an out-and-out fatal attraction.

A fight for an automatic weapon is straight out of “Die Hard.” A relentless assassin could easily pass for the twin of Robert Patrick’s character in “The Terminator.” Eleven enjoys a “Pretty Woman”-like shopping spree. Hopper and Joyce (Winona Ryder) bicker like they were auditioning for “Romancing the Stone.”

Harbour doesn’t have a lot of blockbusters on his own résumé. “Hellboy” bombed and there are no plans for a sequel, he says. A movie he shot in Minnesota, 2011’s “Thin Ice” with Greg Kinnear and Alan Arkin, also sank.

“That’s lucky for me,” said Harbour, who also stars in the Netflix mockumentary “Frankenstein’s Monster’s Monster,” out July 16. “I’m very happy to take it slow and steady and weather things like an unsuccessful movie. I’ve been through it before and I’m still swimming.”

He’s more concerned about his younger co-stars, who are facing the challenge of living up to their early successes and existing in a world where innocence is a precious commodity.

“That’s what I really like about the show, that it pays homage to an America of the ’80s that was sort of a more magical time,” he said. “Because of Twitter and Instagram you’re always aware that somewhere, kids are getting locked in cages. Big, foreboding things are constantly living with us.

“There used to be this sense that kids could get on a bike and spend the whole day in the suburbs not connected to the rest of the world. That sense of getting lost was really nice and liberating.”

His fondness for that era may explain why he’s obsessed about that Tom Selleck seed-art portrait.

“I would honestly pay anything,” he said, still talking about it as he prepared to leave the Science Museum. “That thing is priceless.”