Tre Peart, age 8, read Robert Kimmel Smith’s “The War With Grandpa.” Now a hot 15, living with his moviemaking parents in New Jersey, he’s gotten this filmed and is also its executive producer.

Tre: “My parents always said to read a book before seeing its movie. But this, a school assignment, about a family member moving in and taking over, had no movie. See, I loved the story because that happened to me in Puerto Rico with my grandma.”

In the film is Jane Seymour, Cheech Marin, Uma Thurman, who plays grampa’s daughter, Christopher Walken, who plays his friend, and Robert De Niro as the pushy grampa co-opting the kid’s room.

Says this teen film magnate: “I always loved Robert De Niro. As a young child, I’d always say he’s so great. But I didn’t know the magnitude of getting him.

“In this story, the selfish boy wants to stay in his own room which he loves. It’s uncomfortable. He doesn’t like grandpa who’s trouble and jumps around. Does pranks. Plays dodgeball on a trampoline. So he tries to kick grandpa out of his room until, at the end, they come together.”

Adds this kid who also helped on casting: “I made sure my parents gave me executive producer credit. Also a percentage.”

‘Mission’ in action

Would seem almost a mission impossible for Thomas Cruise Mapother to do his very own death-defying schlep on a motorcycle then mash, crash, dash and smash into a helicopter he’s flying himself, then rush and jump at age 58. Yet Tom Cruise his very own self — as we speak — just checked into Rome’s Hassler Hotel. Film started in Norway. After Rome, Venice. He’s there prepping for scenes in — if you can believe it — “Mission: Impossible 7” or 12. Or whateverthehell this one is.

King’s directing the ring

Clint, Woody, Angelina, Clooney, Affleck, Gerwig, Redford, every movie star since Shirley Temple itches to direct. Comes now Oscar winner Regina King. She picked “One Night in Miami,” a play the NAACP lauded about a 1964 night after Muhammad Ali — then Cassius Clay — beat Sonny Liston and celebrated in a hotel room with Malcolm X. Regina: “Black men, rarely seen as vulnerable, aren’t celebrated on film. This gives the opportunity to respect them beyond their iconic images. Being an actor’s director helps me better understand those vulnerable moments.” Two days left of shooting when pandemic hit. Hoping their film goes gold, they scrambled to finish. Amazon starts streaming it before winter starts snowing.

Personal ‘space’

Hopefully, my talent doesn’t deserve the lavatory, but we now discuss that private space in outer space. Stumping for a perfect loo, NASA just unclogged a new outhouse for the Int’l Space Station. It’s $23 million, 40 percent lighter, 60 percent smaller, 98 percent water-recovery and more resistant to corrosion, which means less maintenance. Listen, we all know how difficult it is to get a plumber — especially in space. I knew you’d want to know.

Pay attention

The Met Opera. Closed for an entire year. Soon organ grinders crank out Roseanne Barr . . . Our 55th governor, David Paterson, said I’m in his new book “Black, Blind, & In Charge” then autographed my copy: “To Sindy” . . . In the old days, the old dames Jackie O and Gloria Vanderbilt lunched in the old Mortimer’s, 75th and Lex. Comes soon Robin Leacock’s book with photos and menus . . . Hollywood dead but Dr. Seuss re-lives. Warner movies cranking up his books “Oh, the Places You’ll Go!” (J.J. Abrams producer) and “The Cat in the Hat.” Comes next W.C. Fields standing in for Kevin Costner?

Since felons now go free, one escapee used a fake gun made from a legal pad’s cardboard and a ballpoint pen’s ink. Our City Hall termed him “armed and ridiculous.”

Only in New York, kids, only in New York.