I think this is the most favorited gif of all time on Imgur.

Reposted here: http://imgur.com/gallery/56dyQ

I'm not sure what the backstory is.

Here's the video:

UPDATE, MARCH 2013: We know more about Stop Girl's back story, thanks to ESPN.

Read to the bottom of this page for more.

Not the official stop girl:

The official Stop Girl:

Imgur comments: Staring contest - Imgur

Above video was put on YouTube Dec 2011 by marketmanable, who doesn't know her.

Game was Sept 18, 2010: http://scores.espn.go.com/ncf/video?gameId=302610012

The Daily Dot has more details:

The game’s tied in the fourth quarter when a camera zooms in on a pretty young woman whose concentration is elsewhere. She’s either stressed or zoned out—until she notices a camera, at which point she breaks into a grin and says “Stop!” (There is ample discussion, it should be noted, of whether she actually says “No!”)

Some people think her name is Amia Miley / Moretti but that is highly unlikely:

Bottom line: no one is sure who STOP GIRL is.

The citizens of Imgur are huge fans of Stop Girl, clearly: http://imgur.com/r/stopgirl

There's a 8600-subscriber stopgirl subreddit: http://www.reddit.com/r/TheStopGirl

StopGirl is also known as TheStopGirl and Ridiculously Photogenic Girl, and this gif has been shared more than 100 times on Reddit according to karma decay.

Her fans would truly appreciate knowing more about her.

If anyone knows more about this woman or this gif, feel free to post here.

UPDATE, MARCH 2013: We know more about Stop Girl, thanks to ESPN.

Read to the bottom of this page for more.

Stop Girl kind of looks like Leighton Meester:

Also, for what it's worth, Imgur is also obsessed with LIGHTS girl:

But her name, we actually know. It's Lights Poxleitner.

And then there's Aine:

Could Emma Stone be the next Stop Girl?

STAHP.

Audrey Hepburn is the original STOP girl:

Creator of this GIF is EditingAndLayout:

http://reddit.com/r/EditingAndLayout/comments/1kf1of/when_i_see_a_pun_thread_thats_actually_funny/

Not quite Stop Girl:

Asian stop girl Jang Ye-won:

http://pandawhale.com/post/46273/asian-stop-girl-gif-gfycat-jang-yewon-from-korea

Stop Girl without Teeth, thanks to Hehelizard of Imgur:

Source: http://imgur.com/gallery/gszWt

Stop Girl with Mustache:

Stop Guy:

Ugh, I don't like where these remixes are going. STAHP!

Here, have some Gretchen Weiners instead:

Also, I don't know how to end this page, so I'll just put a link to Lights:

http://pandawhale.com/post/9212/lights-girl-gif-dat-smile

UPDATE MARCH 7, 2013: Stop Girl has been interviewed by ESPN!

Stop Girl's name is Sarah:

The Stop Girl is Sarah. She doesn’t want to give you her last name, even though she knows “people are crafty,” and will probably sort it out. But you can’t blame her for being a little uneasy. She went to a game and left as a meme.

For the uninitiated, Sarah has become an unlikely, mysterious star on the Internet through no fault of her own. On Sept. 18, 2010, while attending the University of Arizona, she went to watch her Wildcats play against Iowa. An early Arizona lead unraveled, and Iowa tied the game, 27-27, in the fourth quarter. She was not pleased at this development.

To add to her misery, a rowdy student section had been playing to the cameras all game, so she leaned over the railing to get a little distance from her fellow fans.

She saw an ESPN cameraman train his camera on her. Then, to her surprise, the red light came on. As the camera stayed fixed on her, she playfully implored the cameraman to stop, melting hearts in the process.

Somehow, two years later, she reappeared as an animated GIF, a perpetual loop that became increasingly celebrated on reddit, which bills itself as “the front page of the internet.”

There is a whole “subreddit” devoted to Sarah’s animated mood swing, with nearly 12,000 subscribers who do nothing more than post the GIF in response to titles like, “Dear North Korea.” The file has been uploaded many times across many services. But at least one has been viewed about 1.4 million times.

Here's a picture of The Stop Girl Sarah three years later:

Read more at ESPN:

http://espn.go.com/blog/playbook/fandom/post/_/id/19333/reddits-stop-girl-discusses-internet-fame

Why was the Stop Girl GIF so popular?

Her emotion in the GIF is so specific, but also universal. When you’re laughing at something and you don’t want to be laughing at it, and you don’t want to be smiling … that’s universal. It’s never been summed up in an animated GIF so well before.

“And 2012 just seemed to be the right time when the girl smiling and saying, ‘Stop!’ worked perfectly and just kind of stuck around.”

Does Stop Girl say STOP or NO?

Within the context of the reaction itself, there’s even been debate. Some have speculated that The Stop Girl was actually saying, “No.”

Sarah puts that to rest.

“I love the debate over whether I said ‘No’ or ‘Stop,’” she said. “I said ‘Stop,’ because I thought, ‘I can’t yell at this cameraman.’ I guess the whole argument is because my lips didn’t close at the end of the word.”

“OK guys, this is reading into it a little bit too much.”

Does Stop Girl have a boyfriend?

Sarah obviously hasn’t tried to capitalize on the attention. She recently graduated from Arizona and is beginning her career. She said no one seems to have randomly recognized her in public, but she has heard from old friends who realized it was her.

“Some people I haven’t talked to since elementary school have asked, ‘Hey, is this you?’ she said. “One of my friends who’s older said, ‘My sons want to meet you and have dinner. My sons think I’m so cool now that I know Stop Girl.’”

Broderick said the mystery has long been part of the appeal.

“Absolutely. I’ve seen where they’ll be like, ‘Who is this girl? Where is she from?’ he said. “No one knows who she is. It has allowed the fascination to keep going. Once you learn the backstory of the meme, or the background of an Internet joke, it loses a little bit of its fun. It stops being something so spontaneous and weird. It just becomes a normal thing. It allows you to always wonder and always use it and never know the reality.”

So we’re sorry to ruin a little of that fun, but while we’re at it, here’s one more crushing blow from The Stop Girl:

“I do have a boyfriend,” she said.

Sorry, fanboys.

I still don't know how to end this page, so here's another link to Lights:

http://pandawhale.com/post/9212/lights-girl-gif-lights-poxleitner-dat-smile