Astronaut Buzz Aldrin knew exactly what to say Tuesday to impress the 18,000 Minnesota schoolchildren celebrating their volunteer and charity work for the fourth annual WE Day at Xcel Energy Center.

“Did you know I took the first selfie in space?” Aldrin said.

The already hyped crowd, glowing with smartphone screens, went wild.

Aldrin, the American icon who walked on the moon with Neil Armstrong in 1969, was one of the headliners for the polished, stadium-style event meant to reward and inspire the state’s youngest do-gooders.

Started by a pair of brothers in Toronto in 2007, WE Day is a daylong celebration of pop music, dancing and inspirational speeches for young philanthropists. Those attending earn their tickets by volunteering, organizing charity events and helping to raise money for ­nonprofits.

“It’s super exciting and inspiring, said Champlin Park High School Senior Sarah Croteau, whose weekly volunteer work at the Springbrook Nature Center in Fridley earned her a ticket. She feeds the snakes and turtles on exhibit. “I didn’t really know volunteering could be so fun. It’s sparked my passions.”

Last year, Minnesota students under the WE banner completed a million volunteer hours and raised $600,000 for hundreds of charities.

There are now 15 WE Day events across the United States, Canada and the U.K. Minnesota WE Day has attracted thousands of kids and a veritable Who’s Who of adults. Gov. Mark Dayton and state Education Commissioner Brenda Cassellius took the stage briefly Tuesday morning to rally the crowd.

The Twin Cities’ strong culture of grown-up giving is what attracted WE Day ­organizers.

“For all the talk in Minnesota and the pride we have for the amount of philanthropy around here, one of the missing pieces was the next generation. Where is the next Otto Bremer going to come from? What makes somebody like that?” said Brian Lipschultz, trustee of Otto Bremer Trust, one of the events main Minnesota sponsors. WE Day nurtures and inspires that next generation of givers, Lipschultz said.

“It’s about treating kids not just as people who need help, but people who can give help,” he said. “Kids are powerful forces in the world.”

Celebrities step up

This year’s celebrity lineup included pop songstress Paula Abdul, Disney Channel’s teen starlet Olivia Holt, YouTube sensation Lilly Singh and original Star Trek actor George Takei.

But it was Aldrin who seemed to wow the crowd. Aldrin, an 86-year-old West Point graduate, who inspired the character Buzz Lightyear in the film Toy Story, had an immediate rapport with the kids. Aldrin, who served in the Air Force and then in the Apollo space program, talked about a life dedicated to ­service.

“Believe it or not I was once a kid who dreamed big dreams,” said Aldrin, dressed in a “Destination Mars” T-shirt, jeans with suspenders and an arm full of bracelets. “The first time I applied to NASA I was turned down,” he said. “I applied again. Don’t give up.”

He described the swell of pride the American people felt after the moon landing.

“We started with a dream, and we did the impossible. No dream is too high. I believe the impossible can be done again,” Aldrin said.

‘Do something’

The WE movement started modestly in a Toronto basement when a 12-year-old Craig Kielburger read an article about a Pakistani boy living in slavery who was killed for speaking out.

“Like any kid growing up in the suburbs, I didn’t have much awareness of what was going on in the world. I was so angry,” Kielburger said.

He rallied classmates to “do something” to better the world. They met a strong resistance from established charities who saw children as recipients of services rather than do-gooders themselves.

“It was incredibly difficult to find someone to take us ­seriously,” Kielburger said.

With the help of his brother Marc, Kielburger started a charity originally called Free The Children with two main focuses: Doing good in the world and empowering kids to take part.

“We did a garage sale. We did a lemonade stand. We learned what a petition was from a librarian,” Kielburger said.

Oprah Winfrey offered to help them build 100 schools.

The WE organization has grown into an international nonprofit that since its first WE Day in 2007 has raised $79 million for 6,500 causes and logged 27.6 million hours of volunteer work through its schools program.

“It’s nice to have something that inspires and renews your faith in humanity,” Kielburger said. “The world is a good place. There are good people who are doing good things in the world.”