HUMBLE, Texas >> Jason Dufner was sitting in a classroom with children for a charity event when he leaned against a wall and zoned out for a minute.

That’s all it took for one photo that went viral and made Dufner a Twitter sensation.

Dufner, dressed in a red golf shirt, is shown slouched against the wall at J. Erik Jonsson Community School in Dallas, next to two children who are listening intently to the teacher. His legs are erect, his arms stiff at his side, and he has a vacant look on his face. Dufner is known for showing little emotion, even with a major championship at stake. He looks even more lifeless in this photo.

“Just caught me at a perfect time,” Dufner said Friday from Auburn, Ala. “The funny thing about it is the photo taken represents how I act all the time. It was a sheer moment of ‘Jason Dufner’ by whoever captured the moment for the 30 seconds I checked out.”

That would be Christine Lee of KXAS-TV, a video journalist for the NBC affiliate in Dallas who was covering Dufner’s appearance at the school.

Dufner won the Byron Nelson Championship last year. The Salesmanship Club of Dallas, which runs the tournament, directs some of its charitable proceeds to the school for disadvantaged children. To drum up publicity as the defending champion, Dufner made an appearance at the school Thursday.

He never imagined where it would lead.

Lee took a photo of Dufner in that perfect moment and gave it to sports anchor David Watkins, who posted it to Twitter.

Among those who saw it was Keegan Bradley, who beat Dufner in a playoff for the 2011 PGA Championship and has been engaged in friendly banter over the last month. And it took off from there.

Dufner’s name became a verb. It’s call “dufnering.”

Luke Donald tweeted a photo of a pillow under his shirt as he slouched against the wall in his home. Rory McIlroy was dufnering in his hotel room, and he couldn’t stop talking about it Friday at the Houston Open. At one point in his round, he walked behind the 13th green, saw a reporter and said, “Did you see the Dufner photo? How good is that? That’s the greatest thing I’ve ever seen!”

Bubba Watson was dufnering against his General Lee 01 car. Dufner even got in on the act Friday, dufnering in the weight room at Auburn.

Those who think it’s an example of a professional golfer who couldn’t be bothered spending time in a classroom with children were missing the point. Dufner always looks that way. Even in the PGA playoff at Atlanta Athletic Club, he didn’t appear to have a pulse.

In an era when players don’t always return to the cities where they won, Dufner participated in two media days in one week. He was in New Orleans on Wednesday (the Zurich Open was his first PGA Tour win), and then headed to Dallas for the classroom.

The subject?

“They were talking about focusing and relaxation,” Dufner said, a master at the latter. “They have some big test coming up for the class on ways to relax and concentrate. And I guess I took it to another level.”

After all the Twitter photos of people “dufnering,” the man himself finally replied.

“What can I say, I was tired, my back hurt from sitting on the floor, and we were talking about relaxation and focusing. (hash)dufnering” he tweeted.

By then, it was all the rage.

Dufner thought nothing of the charity event until he arrived at the airport and noticed the photo had been posted on Deadspin. Bradley took over from there.

“Every time I looked at it, I laughed harder than the first time,” Bradley said from the Houston Open. “Dufner is so funny with some of the things he does. That’s him.”

Bradley said he has never seen his Twitter account fill up with thousands of pictures and responses, and he was stunned to wake up Friday morning to see that “dufnering” was trending on Twitter, especially during the NCAA basketball tournament and American idol.

When he arrived at Redstone on Friday morning, he got together with Dustin Johnson and Brandt Snedeker for a “dufnering” pose by the putting green.

“I saw a basketball player doing it in the locker room,” Snedeker said. “I never knew Dufner had such a wide range of appeal. His personality is not a welcoming personality. But once you get to know him, he’s actually one of the funniest guys you’ll ever meet. He just doesn’t give you anything on the golf course.”

Snedeker’s impression of the photo?

“It looks like someone put him in timeout,” he said.

Dufner, however, figures he’s getting the last laugh. Hardly anyone knew who he was two years ago. Then, he lost a four-shot lead with three holes to play in the PGA Championship and wound up losing to Bradley in a playoff. He handled the loss with dignity and — as always — no emotion. A year later, he won in New Orleans and Dallas in the span of a month, and played on his first Ryder Cup team, winning three of four matches.

“I think Keegan tried to use it against me but it blew up in his face with all the publicity,” Dufner said with a chuckle.

So what’s next? Dufnering at Augusta National during the Masters?

“Oh, for sure,” McIlroy said. “I would ‘Dufner’ on the lawn. No. On the tree out back by the clubhouse.”

About the only person not caught up in all the hype is Dufner’s wife, Amanda.

“She gets to see me ‘dufnering’ the most,” Dufner said.