NOTE: You can watch "The Green Guys" and thousands of other runners cross the finish line at this year's watch right here on the NBC 5 website and app.

If you’ve watched or run the Bank of America Shamrock Shuffle, chances are you’ve seen “The Green Guys.”

They’re the ones covered in green body paint, wearing green running gear, green wigs and even green sunglasses – while running an 8K.

But who are the runners behind the costumes?

We spoke to the group kicking off outdoor running season in Chicago in style each year to learn more about how it all started and what goes on behind the scenes.

John Atchison, a physical education teacher in Chicago, is the mastermind behind the getup. He started “The Green Guys” with a friend during an “Unofficial St. Patrick’s Day” at the University of Illinois in 2008, he said.

“We had so much fun running around the campus in our strange getup that we decided to run the Shamrock Shuffle as ‘The Green Guys,’” he told NBC 5 via email. “I have always been known to do wacky things, but I had no idea how much this idea would stick.”

Eleven years later, Atchison is still running in costume, now flanked by an even larger group of people from around the Chicago area.

This year, Atchison will be joined by his wife Brittany, and eight others - Oscar Munoz, Andres Ardila, RJ Puoci, Eric Nguyen, Mark Hode, Matthew Jeromin, Nathan Tamayo and Trina Tamayo. In addition, decorated wheelchair athlete Amanda McGrory has also joined the group, crossing the finish line first in 2018 decked out in the iconic costume. 

But the group’s size isn’t the only thing that’s changed in the races since.

“Over the years the costume has evolved. It wasn’t [until] the third year that I realized sunglasses are crucial.” Atchison said. “It also took [until] the third year to realize that painting in a bank parking lot outside in 30 degrees is an awful experience. Thus, came the era of staying the night in either the Congress Plaza or Hilton hotel. By year four I began sharing ‘The Green Guys’ experience with my close friends.”

Among the new group of runners is a Shamrock Shuffle veteran, who has been running the race since 2011 and joined the group just last year.

Jeromin, 38, of Rolling Meadows, said donning the costume takes the energy of the race to an entirely new level.

“People respond positively to the sight of the green guys,” he said. “A lot of people love to give high fives and pose for pictures and just all around have fun.”

That’s echoed by fellow newcomer, 27-year-old Mark Hode, who is in training to become a professional pilot.

“Most of the time, these races are so serious for us because we like to compete,” he said. “This is one of a couple races where we just get to have fun and enjoy the event, interacting with other participants, while painted Green in the best city in the world.”

But it’s not exactly easy being green.

The group typically gets up around 3 a.m. on race day, with painting taking about 45 minutes.

“We pile three to four people into a small bathroom and sometimes someone in the tub,” Atchison said. “We paint and make fun of each other all in good fun.”

The group then puts on their running attire and heads to the starting line prepared to high-five, stop for dozens of photos and enjoy a good race.

“After the race we go back to the hotel and clean up the bathroom, cause that is a mess, and the shower process begins,” Atchison said. “It usually takes at least five showers for all the paint to come out. Although my students often ask me if I painted my nails throughout the week as that is the hardest to get clean.”

But for “The Green Guys,” it’s all worth it.

“Getting to dress up with them promotes a fun, healthy way to enjoy this fabulous city and other Chicagoans,” said 43-year-old Trina Tamayo, a nurse at Advocate Lutheran General Hospital. “And that no matter the color of our skin- brown, black, white, green - we can all come together as one and enjoy each other’s company, or feel each other’s pain for those that are not runners.”

So, what’s their advice to runners taking on the Shuffle this weekend?

“My message for other runners this year is to enjoy the day with friends and family,” said Hode. “Make new friends out there, these races are a great way to meet new people and to hear and learn about others stories about what they had to do to get ready to race that day. And most importantly, if you see us 'Green Guys' coming, cheer us on, stop us for a picture, say hello, do anything! We are there for you.”

“My advice would be to not get too carried away with the start, which is easier said than done,” said Jeromin. “When that starting gun goes off, it’s like being a part of a stampede, and that coupled with the nerves, generally leads to a super fast first mile.”

“Go out and have fun,” said Nathan Tamayo, a 39-year-old embalmer from Park Ridge. “How many times do you get to run around downtown Chicago? Treat it as a race to gauge where you are right now and how much work you need to put in for the summer races.”