The soon-due movie “The Butler” features every familiar name but Dumbledore. At its celebrity-clogged premiere, one unknown huge bear in a black porkpie hat lumbered around hugging everyone. So I asked, so who are you?

Kevin Ladson.”

What’s a Kevin Ladson?

“I was the prop man, and with history and eight presidents I had to see that all was exactly right.

“Each president has a library. I checked everything with the Kennedy Library, Reagan Library, Eisenhower Library, Nixon Library, all of them. The 6 1/2-month research went even to the individual special tie clips each president’s personal staff wore. I was given one. But all had to be returned — including mine.”

Kevin, weighing like an SUV, clutched his own lone prop. A bottle of water. Looking to lose a few? “Hey, I’m tryin’,” he laughed.

Another getting acts and facts together’s Admiral Stephen W. Rochon, Dubya and Obama’s White House director. His son Omari played a chef in the film.

“I checked the movie sets,” he said. “Oversaw each item in the Oval Office, positions of everything in the East Room, flowers at the state dinners, how the butlers positioned themselves. Each did different things for their presidents.

“The re-creation of the second floor staircase into the State Dining Room was incorrect. It went in the wrong, opposite direction. Curved left instead of right. But the entire set had been constructed, camera angles and action already mapped out, so it couldn’t be righted.”

Getting lost finding the theater’s entrance, the admiral grinned: “Well, there’s no water around to guide me.”

Wil Haygood is the writer who found the actual living butler who’d served these eight presidents: “He had this archive. He said to me, ‘Nobody’s ever done a story on me.’ Took me 57 phone calls to find him.”

New Yorkers: kindest of angels

Sunday, 5 p.m. Downtown. Corner of Houston and Greene. Lena Dunham desperately stressfully needing a taxi. Accountant Alexander and his friend Dmitry helped the sister out.

They tweeted: “Let us hail you a cab,” and signed, “the two male homosexuals.”

Spotting an empty one chugging down Houston, they nailed it and handed the vehicle over to her.

Huggy, kissy Lena then tweeted back: “To the two male homosexuals who hailed me a cab today on Houston Street, then hugged me and disappeared . . .

Thank you. Are you angels?” And later: “You truly made my month! You were handsome, magical, and then you were gone. This is why I love NY — and Twitter.”

So, don’t nobody ever say NYers are rude and not helpful.

Odds & ends

“Star Wars” genius George Lucas prepping the next generation. Mentoring young American Film Institute hopefuls . . . Come fall, Greg Kinnear’s new TV series is Fox drama “Rake” . . . “Dancing With the Stars” Derek Hough dances Monday in Central Park’s Bandshell. For SearsStyle Jean Scene . . . Catsimatidis taking time from running for mayor to run Sept. 19 to Chelsea Piers’ Police Athletic League Sports Night.

Midtown East. The upper 40s, lower 50s. Reader Marilyn Wright’s neighbor, “sweeping the pavement, started to toss away a little coin. Suddenly it wiggled and out peeped a tiny head. Placed in a pond, this newly live coin turned from gray to green. The neighborhood was thrilled to realize they’d saved a life.

A live turtle in Turtle Bay.

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