This is the face that launched a campaign to save some of America's most vulnerable dogs.

"She looks like a punk rocker, but she acts like a nun," said Brandon Stanton of his dog, Susie.

Stanton, with his girlfriend Erin O'Sullivan, is the man behind the wildly popular blog, " Humans of New York," which features photos and stories of interesting New Yorkers.

He met Susie while on the job.

Susie, 13, above, from "Susie's Senior Dogs." Credit: Brandon Stanton

"I had never seen a dog that was that interesting," Stanton said. "I called her the greatest dog in New York."

Related: One woman's quest to save dogs' lives with a camera.

Stanton posted a photo of Susie to HONY and Susie's owner saw it. A week later, the owner came up to him and asked Stanton if he wanted the dog.

He ended up adopting her despite her age - she's 13 - and they fell in love.

"She's old, and she's attached," Stanton said of Susie. "She wants to be with me everywhere."

"She loves him so much," said O'Sullivan.

Susie is lucky. Most people prefer puppies when adopting dogs and older dogs have a hard time finding a home.

"The alternative is to either be in a shelter, or even worse," Tiffany Lacey of Animal Haven, an animal shelter in New York.

Related: How to adopt a stray dog from Sochi.

Despite that fact, senior dogs actually have a lot going for them.

"If you're just looking for…someone to completely love you, the senior pet is the way to go," Lacey told ABC News.

So O'Sullivan decided to take up Susie's cause. She started a Facebook page, " Susie's Senior Dogs," to find aging dogs new families.

Stanton posted it and it went viral. The first dog, 13-year-old Nina, was adopted in just two days.

Nina, 13, with her owners Jesse Simon, right, and Moira Foehr, left. Credit: Jesse Simon and Moira Foehr

"She brings a lot of happiness to the house," said Jesse Simon, one of Nina's owners.

"I think that's because she's a senior dog," Moira Foehr, Nina's other owner, said. "She's been perfect."

"It started informally without any kind of plan" O'Sullivan said of the Facebook page, which launched at the end of January. "I wasn't expecting for dogs to get adopted right away."

But " Susie's Senior Dogs" has had more than 20 success stories so far.

Max, 10, adopted in Virginia Beach and Rosco, 6, adopted in Oregon are among the lucky ones.

Max, 10, above, lives with his owners, Amanda and Matt, in Virginia Beach, VA. Credit: Amanda Novak

Rosco, 6, above, lives in Oregon. Credit: Mark and Katherine Dobney

"I don't want it to be all talk but talk and action," O'Sullivan said.

There are many dogs that are still waiting to be adopted, including Heartthrob, who is up for adoption at Animal Haven in NY.

Heartthrob, above, is up for adoption at Animal Haven. Credit: Erin O'Sullivan/Susie's Senior Dogs

One funny little dog's face turned into one big viral movement - saving lives, in that classic "America Strong" tradition, by rooting for the underdog.

The dogs featured in this story were adopted from these shelters:

ANIMAL HAVEN - New York, N.Y.

CLATSOP COUNTY ANIMAL SHELTER - Warrenton, Ore.

VIRGINIA BEACH ANIMAL CARE AND ADOPTION CENTER - Virginia Beach, Va.

LONG ISLAND PIT STOP ANIMAL RESCUE - Huntington Station, N.Y.

CRITICAL CARE FOR ANIMAL ANGELS - Warner Robins, Ga.

ABC News' Jennifer Metz contributed to this story.