The school bus rolled up to a retreat center on a lake in rural Minnesota, and out stepped a clown. And another. And then another. They just kept coming.

It wasn’t a mega-sized clown car gag, but the arrival of campers from all over the country to Mooseburger Clown Arts Camp, the pre-eminent weeklong training program that educates clowns in the art of funny business. Called Moose Camp for short, the annual gathering is in its 19th year, and runs through Sunday in Buffalo, Minn.

Adorned with sequins, rainbows, polka dots, bows and flowers, the campers embraced the longtime staff members and immediately began joking around, like a family reunion where only the hilarious uncles showed up.

“This is like ‘March of the Penguins,’ ” one staffer said, while a man in oversized clown pants strolled past toward check-in.

This year’s 75 attendees were about to embark on a mini clown university, where they could choose majors in topics like puppetry, comic writing, hospital visitation and magic, and electives in face-painting, balloon-tying, miming and juggling. Extracurriculars: a “red-nose prom” and a massive pie fight.

Ever wondered how a clown’s makeup survives a pie in the face? Or wonder what those pies are really made of? All was revealed within the first hours of camp.

For many students, a highlight of the camp is a public performance in which the clowns can put their new skills to the test. The All Star Clown Show is at 6:30 p.m. Saturday at the Buffalo Civic Center. Admission is free.

The coursework takes place at a Catholic retreat center, where 6-foot wooden cutouts of clown faces are propped up next to religious icons and the smell of incense pervades the clown makeup lab. A small auditorium is transformed for the week into the “dealer’s room,” where patrons can purchase classic clown videos, red noses, arm-length bow ties and punny props. (A plastic cup with a tiny wooden stool inside? Stool sample.)

At the heart of Moose Camp is Tricia Manuel, a former touring clown with Ringling Bros. circus and a costume designer with a shop in Maple Lake. Her alter ego, Pricilla Mooseburger, is one of the most recognizable names in clowning, not only for her renowned costume work, but for the community she has built over 19 summers.

“This is a family here,” said Terry Ricketts, a clown from Mesa, Ariz., who teaches prop-making. “We all love each other, and we look forward to it all year long.”

A rarity

Moose Camp is one of the only programs of its kind. Ringling Bros. offers a clown college for young adults who want to do the old “run away and join the circus” thing, and there are plenty of one-day classes around the country. But here, people of all ages get to immerse in their art for a week.

“Mooseburger has really defined the market,” said Greg DeSanto, director of the International Clown Hall of Fame in Baraboo, Wis., original home of the Ringling brothers. “You put your regular life to the side for a few days, and it’s a gift you give to yourself.”

Participants range from the college-age offspring of elder clowns to retirees finally following their childhood dreams.

“A lot have been bullied and come from a place of being misunderstood,” said Manuel, aka Mooseburger. But in full garb on a parade route or at a nursing home, they get to feel “like a rock star.”

“They don’t care about the social stigma” of being a clown, she said. “When you find your tribe, you find your own kind.”

The stigma that clowns are “creepy” (thanks to Stephen King), don’t talk and have to follow a strict set of rules doesn’t apply to this creative bunch who set their own agendas, she said. One thing all clowns do have in common is a willingness to make fun of themselves.

“You sacrifice your pride to be the butt of a joke,” she said.

That humility extends to life out of costume, too. Moose Camp seemed to immediately wrap its arms around newcomers — including beginner clowns. Manuel, 54, even unofficially adopted a teenage clown-to-be who didn’t have a family; he now tours with Ringling along with Manuel’s two daughters.

Newbie Sara Stearns, 30, watched wide-eyed as a spontaneous dance party turned into a hug fest after the 30-member staff put on a variety show for campers on the first night. The shy Minneapolitan had always dreamed of being a clown but made excuses why she couldn’t pursue it. Then her husband found Moose Camp online and signed her up.

“I thought I was going to be freaked out, but everybody is so, so nice,” she said. “It’s like you’re amongst your own kind. Like you’re at home.” Minutes later, she was swept into the center of the bewigged and polka-dotted throng.

Teen’s summer camp

Nathan King, 15, found his people last summer, the first time he attended Moose Camp. Now, he’s back, and he’s even got his mom Cindy taking face-painting classes and filling him in on what he missed. (An adult chaperon at the camp is mandatory.)

Back home in Branson, Mo., Nathan performs at birthday parties, in parades and has even managed to “talk his way into” the traveling circus when it came to town. He’s got his own business card for his persona, Woody the Clown, who he says is an “extension” of himself (“over-the-top dramatic, a flirt, an all-around good guy”).

Nathan knew since he was 12 that this was the path for him.

“You have to be called to it,” he said.

What does he love about being a clown? “Just the fact that somebody can remember me forever, the fact that I can make somebody’s day go from the worst day to the best day and just the fact that I can make this world a better place through this wacky thing that I think is fun.”

The first evening of camp, the staff staged a performance inspired by the best of the vaudeville era: corny magic tricks, a slapstick clown makeup lesson involving bananas and two cartons of eggs, a father-and-daughter routine and a delicate ballerina puppet gliding to “La Vie en Rose.”

Nathan sat cross-legged on the floor just in front of the stage, looked up at his mentors and laughed with his whole body at every gag.