Someone's stray dog quickly became another man's most treasured friend.

Twelve years ago, Brinks' previous owner decided that he didn't want the pit bull anymore. He was only a puppy, between 10 and 11 months old.

"Apparently he had been left at the school playground the night before by somebody," Jon Bozak, Brinks' rescuer, told The Dodo. "He was never mistreated. Somebody just decided to give him up. My neighbor told me years later that he had seen Brinks wandering that night."

Bozak met Brinks the next day. He was leaving his New York City apartment that morning, which was situated right in front of the private school where Brinks had been abandoned.

"There was this big pit bull across the street," Bozak said. "He saw me and my dog, Demo, then came trotting over."

Bozak wasn't in the market for another dog — he felt that he already had his hands full with Demo, who was an older pit bull. Furthermore, Bozak said, Demo could be finicky about which dogs he got along with.

But when Brinks approached Demo, the two greeted each other by smiling at one another in the way dogs do, and Bozak realized they would get along well enough.

There was another thing about Brinks that Bozak noticed very quickly as well.

"As soon as I put him in the car, he sat in the front seat, pretty much ignoring me," Bozak said.

"He was just looking out the window. Then he started smiling. I was like 'This is crazy, this dog is grinning. This is nuts.' I didn't want another dog. I figured another 65-pound pit bull was going to be a lot to handle. But Brinks was too awesome to be true."

After putting up flyers around the neighborhood to make sure someone wasn't desperately looking for Brinks — and getting no response — Bozak decided to become Brinks' new dad, making him a permanent member of the family.

"Honestly, he really does smile and grin," Bozak said. "It's definitely a submissive type of grin. But it's also a happy grin at times. If you put a treat in front of him, he's going to grin. If he's sleeping next to you, he's got a grin on his face while he's sleeping."

Bozak noted that Brinks is a very communicative dog — and his smiles say it all. He lived with Bozak's other dog, Demo, for six years before the older dog passed away. Now Brinks is an "only child," but Bozak doesn't worry too much about how Brinks is faring.

The pit bull will be turning 13 years old in December and he's as joyful as ever.

"He's the most confident dog I've ever been around," Bozak said. "Brinks has the best life and I think he appreciates it. It's nice to have a dog who's so happy."

Keep up with Brinks and all of his wonderful smiles on Instagram.

Watch this video about a dog and baby who love cuddling together: