When Stephen King got the call to come back to Derry, he reacted like a typical Loser—resistant at first, trying to bargain his way out of the idea. But finally he accepted that it was the right thing to do.

That’s how the father of Pennywise the Dancing Clown turned up in a scene-stealing role as a grumpy shopkeeper in It: Chapter Two. And now that the film has opened to $185 million at the global box office, King is telling the story of his involvement in the sequel, including his thoughts on one of the major additions it made to his original 1986 novel.

King, who turns 72 later this month, didn’t appear in 2017’s It; he has little interest in rivaling Stan Lee or Alfred Hitchcock’s litany of creator cameos, having significantly cut back on his screen appearances over the years. He prefers to focus on writing, and has a new book, The Institute—about psychic children who are forcibly rounded up by a sinister organization—hitting stores on Tuesday.

The author was lured to the It: Chapter Two set last year by two things: director Andy Muschietti’s concept for the cameo, a timeline-jumping idea that was ultimately abandoned, and the opportunity to be a total jerk to best-selling writer Bill Denbrough, played by James McAvoy—hitting him with some of the drive-by negging King himself has endured from armchair critics over the years.

“Yep,” King told Vanity Fair with a laugh. “It was a huge pleasure to do that.”

In the film, King plays the bespectacled proprietor of Secondhand Rose, a consignment store where Denbrough discovers the rust-flecked remains of Silver, his beloved childhood bicycle. The shopkeeper instantly recognizes Denbrough as a popular author, knows he has a lot of money, and intends to get as much of it as possible for that beat-up old bike. Sentimental value can have a steep price.

When Denbrough offers to conclude the transaction by autographing one of his books, the shopkeeper not-so-politely snaps that he doesn’t care for Denbrough’s endings. (Shots like those really do irk King, even to this day.)

But apparently this is not the first time the Secondhand Rose owner has crossed paths with Denbrough. Muschietti confirmed that originally, the film planned to have King’s shopkeeper show up in a flashback, interacting with young Bill (played by Jaeden Martell) and his friend Beverly Marsh (played by Sophia Lillis).

“When Bill Denbrough walked into the thrift shop, he had a flashback of him and Beverly browsing the same place 27 years ago,” Muschietti said. “It was a little romantic moment there, and then they were approached by the shopkeeper as a younger version.”

There would have been no digital de-aging for King, however. Instead, the younger shopkeeper who ruins their tender moment would have been played by King’s son, author Joe Hill.

“Andy’s original idea was so genius,” King said. “He wanted to use Joe as that guy in a flashback with the kid, and it would’ve worked because Joe and I look a lot alike.”

Alas, the idea was never shot. “We started with a script that was 160 pages, and that was the short version,” Muschietti said. “Unfortunately, we had to shave it off. It was impossible.”

But the author remained committed to the cameo, despite his early qualms. “Andy asked me if I’d do that, and the major thing for me is: How hard is it going to be to get there?” said King, who doesn’t like to travel often. Fortunately It: Chapter Two was filming just over the border from Maine—and curiosity from another generation also led King to participate: “They were shooting in Port Hope in Canada, and it was really just a hop. So I went up with my grandson, who’s crazy about movies—the oldest one, Ethan—and we hung out on the set. It was cool.”

Still, King couldn’t help cautioning the filmmaker in a last-ditch effort to escape the camera. “He said, ‘Actually, you have to know that I’m a jinx,’” said Muschietti, breaking into the author’s Maine accent by way of the filmmaker’s Argentine one. “Apparently all the movies that he was in with a cameo ultimately bombed. He wanted to warn me. I said, ‘I don’t think we need to worry about that. We can avert it. We can lift the spell.’”

King even did some writing on set, crafting dialogue full of words beginning with B to provoke Denbrough’s stutter. “He was part of the creation of that scene. It just happened on the day,” Muschietti said.

Before that, the author also weighed in on the script by suggesting a few elements from the original novel he wanted to see onscreen. One of them was the town of Derry’s tacky Paul Bunyan statue coming to life to terrorize grown-up Richie Tozier (played by Bill Hader), which Muschietti did include in Chapter Two. The other was a desire for Derry’s towering water standpipe to roll down a hillside in the finale of the film, when an otherworldly storm walloped the community.

The town is nearly wiped off the map in the book, but Muschietti didn’t want to end on that note. So there wound up being no supernatural storm. “I wanted to keep it emotional rather than going for a huge, Hollywood destruction ending,” the director said.

As part of that more heartfelt finale, Muschietti and screenwriter Gary Dauberman also added a character beat that reframes the entire relationship between “Trashmouth” Tozier (played as a kid by Finn Wolfhard) and Eddie Kaspbrak (played as an adult by James Ransone and as a kid by Jack Dylan Grazer.) In one of the final images of the film, the audience learns Tozier harbored a secret, unrequited crush on his friend, and has been struggling his whole life to accept his sexuality, using his sarcasm and wisecracks as a shield.

In King’s original novel, a young gay man named Adrian Mellon is brutally murdered—a killing inspired by a true Maine hate crime. That same scene opens It: Chapter Two, showing how cruelty and fear can nourish more of the same. King liked the Richie addition as a bookend for the movie, even though he admits that he didn’t build an element of unrequited romance into Eddie and Richie’s relationship in the book. “No, I never did,” King said. “But again, it’s one of those things that’s kind of genius, because it echoes the beginning. It comes full circle.”

Though both stories end tragically, they stand in contrast to the ugliness and cruelty fostered by Pennywise. “At least there’s love involved. Somebody cares for [Eddie,]” King said. “And that echoes the love that Adrian’s partner has for him. So that was cool.”

King hopes It: Chapter Two will bring people closer together, in a literal sense. “Andy is brilliant when it comes to creating a horror scenario. He knows what scares people, and he also has a sense of humor,” King said. “It —both chapters of It—are fun. They’re scary, and you holler, and you scream, and you clutch whoever you’re with—but you also laugh.”

Unlike his disagreeable shopkeeper, King likes to leave the customer with a smile.

— Our cover story: Lupita Nyong’o on Us, Black Panther, and much more
— Five appalling stories from the set of The Wizard of Oz
— Hugh Grant’s very English comeback
— How’s Joker? Our critic says Joaquin Phoenix towers in a deeply troubling film
— Lori Loughlin finally gets a win

Looking for more? Sign up for our daily Hollywood newsletter and never miss a story.