Conductor Patrick O’Brien, in a formal train conductor’s cap, long black coat and black leather gloves, urges the children — all dressed in Christmas pajamas — to pull themselves together. They’re about to arrive at the North Pole, and they need to show the proper respect.

“I don’t want any cowlicks! I don’t want any messy hair! I don’t want any untied shoelaces!” O’Brien orders. Then he warns passengers about the temperature they’re about to experience: “When we get to the North Pole, it will be 128 degrees below zero.”

“Why aren’t we flying?” asks Grace Murphy, 5, of Babylon. “Because the North Pole is on the top of the world.”

“She’s got a point,” says James Maloney of Massapequa, looking out the window at the East End of Long Island as their North Fork Trolley trundles down the road. He’s traveling with daughter Kaitlyn, 4.

Oh, ye of little faith! Believe! Passengers may have boarded in Riverhead, with O’Brien punching a hole in their golden tickets, but they’re arriving by holiday magic on Long Island’s Polar Express.

“Welcome to the North Pole!” O’Brien, 19, a Suffolk Community College student from Riverhead, bellows as their trolley parks. “I do have a few rules. Drink the hot chocolate. Eat the chocolate chip cookies. Talk to Santa. Take lots of pictures.”

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MOVIE, BOOK COME TO LIFE

Three years ago, Tom Ingald, a co-owner of the North Fork Trolley Co., added the Warner Bros. Polar Express experience license to his business. The experience, offered nationwide, is based on the book and movie. This year, Ingald and business partner Jay Mooney offered about 250 trolley trips between the day after Thanksgiving and Dec. 23. All sold out well in advance, with more than 6,000 people riding.

Most riders — especially the kids — already know the story of a boy who, while in his pajamas on Christmas Eve, is picked up by the Polar Express train. He uses a golden ticket to travel to the North Pole, where he asks Santa for a jingle bell from his reindeer, whose ringing only people who believe can hear.

So they chatter in excitement on the ride, while a recording of the story plays in the background. When they arrive at the North Pole, Santa is attended by elves dressed in jester-like red and green costumes and a cook in a white chef’s hat offering hot chocolate and chocolate chip cookies. Cook Cindy Kasper, a science teacher at Patchogue-Medford High School, adds extra chocolate mix to make it thicker. “It’s supposed to be just like a melted candy bar in the story,” she says.

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Each child has a sit-down with Santa. Kaitlyn asks for a snowman pillow. Then Santa magically pulls something from behind Kaitlyn’s ear and hands it to her. “My jingle bell!” Kaitlyn exclaims, the bell in one hand and a cookie in her other.

Brenna Kurka, 4, of Nesconset, tells Santa Claus that she is giving up her pacifiers, and that she’ll be leaving them for him on Christmas Eve. She has brought one that she hands him. “This here is our binky box. Let me take it and put it right here,” responds Santa — aka North Fork Trolley Co. co-owner Mooney, 52, of Wantagh. (“You’ve really got to think on your feet,” he says later about his instant conjuring of a binky box.)

“I got to see Santa! I got to see Santa!” Brenna shouts, jumping up and down in glee and rattling the jingle bell Santa Claus gave to her. “How did he get it behind my ear?” she asks in wonder.

Meanwhile, three elves lead a holiday version of Simon Says. “My elf name is Dazzle,” says Shay Jackson, 16, a Riverhead High School junior. “Elf says, ‘Be a reindeer,’ ” she commands, putting a hand up to her nose and opening and closing her fingers like a flashing light. “Elf says, ‘Make snow angels,’ ” she says, flapping her arms up and down like a bird flying.

On the way home on the trolley, kids and adults alike sing along with a soundtrack of holiday songs. To “Rudolph the Red-Nosed Reindeer” they ad-lib fun lines. “All of the other reindeer used to laugh and call him names,” they sing, then shout “Like Pinocchio!”

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“I thought it was great,” says Flavia Gonzales, 37, of Farmingville, who made the trip with her husband, Randy, 37, and their son, Nicholas, 4. “Just to see the smiles on his face was enough to make Christmas.”