Cullen Byington is still not quite sure why he decided to take a photograph of himself with the big red balls outside of Target stores every day for a year.

But he spurred people across the country to take their own selfies with those round concrete barriers in an offbeat viral phenomenon that became known as “Target balling.”

“If you search the hashtag on Instagram, there over 2,000 pictures from people around the country taking the selfies,” said Byington, 32, of Birmingham, Ala. “It’s crazy.”

People sit on the red balls. They stand on them. They do yoga on them. They lie down on them like they’re Superman. And then, they post pictures to Twitter and Instagram with the hashtag #targetballing.

But no one has brought the same level of dedication and imagination to the practice as Byington, who since early last year has made a living documenting his life in daily videos he posts to YouTube.

He transformed Target’s red balls into Snow White’s ill-fated red apple, a red dot in a Pac Man game, and the wrecking ball from Miley Cyrus’ hit song. For the latter, he donned white shorts and a tank top and posed with pursed lips on top of the ball with a chain wrapped pole on top of it. His wife, Katie, often was the photographer or accompanied him in the pictures.

“It turned into a challenge for me to one-up myself,” he said.

As Target balling began to build some traction, Byington upgraded from his iPhone to a camera, tripod and remote. He scoured his house for props like treadmills and air hockey tables. And he rummaged through his closet and those of his friends’ to find castoff Halloween costumes. After securing a Cap’n Crunch outfit, he made a picture in which he pretended one of the red balls was the “world’s largest crunchberry.”

This is not the first time the Minneapolis-based Target has been swept up in a viral movement outside of its control. Last year, a Target cashier became a Twitter sensation when a picture of the young man with Justin Bieber-like looks became a trending topic on Twitter under the hashtag #AlexforTarget.

Byington even did his own take on that, with a picture of himself in a blond wig and an oversized “Alex” nametag.

Target doesn’t officially endorse the Target ball selfies. But officials became amused by the phenomenon and included a write-up about Byington on the company’s blog last year.

“We absolutely love that Katie and Cullen have so much fun with the bollards,” said Katie Boylan, a Target spokeswoman. “But we need to be a little bit careful about encouraging people to have fun with them. They are 400 pounds of concrete. So you can see where it could be easy for folks to get hurt.”

Bollards are common outside many buildings to protect entrances from being crashed into by runaway cars. In many cases, they are short black or concrete-hued poles that blend into the landscape. Wal-Mart has short blue poles outside its stores. A few people have taken pictures with them in the hopes of starting a similar online phenomenon, but that has yet to take off.

When Target started adding bollards outside its remodeled stores in 2004, it did so with a little more pizazz. It made them red and round, playing off the retailer’s signature color and bull’s-eye logo.

“What other store has big, random red balls in front of their store?” said Alex Hill, a 26-year-old Utah man who took Byington up on the daily Target balling challenge.

He recalled how his daughter would often run up to the red bollards when she was a toddler to hug them and give them a kiss.

Byington and Hill discovered logistical challenges during their year of Target balling. For starters, they quickly learned that not every Target store has the bollards outside. Only about 1,000 of its 1,800 stores do.

And it wasn’t always possible to run to a store every day, such as when their wives were giving birth, so both men kept a reserve of pictures for those situations. As the year went on, both men found themselves heading out to the store later and later, sometimes at 10 p.m. or 11 p.m.

“I started getting into this funk where I had so much other stuff going on,” Hill said. “And it did begin to take a toll on my wife.”

But the encouragement from their followers on social media helped keep them going.

Katie Byington came up with a rule to keep Target balling from overtaking their lives. They would not do elaborate photos with costumes and props on the weekends, but would instead take quick photos, giving those days the nicknames “simple Saturdays” and “selfie Sundays.”

“It was fun and I’m going to miss it,” she said. “But it was also something that I was like, ‘Oh my gosh, I can’t wait for this to be over.’ ”

But for a year, Target balling was a preoccupation in their lives.

It was where they went on New Year’s Eve. It was their first stop from the hospital when they brought their newborn baby home. And it was where they went in the middle of the night after Cullen’s father, who made some cameos in Target balling pictures, died.

And while it started off as more of a silly project, it evolved into something more sentimental and personal.

So when they gathered last month for their final Target balling picture to cap off the year, it as a bittersweet moment.

The Byingtons invited their fans to join them for the final picture. More than 130 people showed up, including one woman who drove five hours from Pensacola to be there.

“It was incredible,” Byington said. “But it was also a relief because I didn’t have to get out of the house the next night.”