Picture the soft, fawn-colored fur and tiny paws of a typical Chihuahua. Take his bat-ears and add a little floppy fold. Stretch the whole dog, snout and all, and add the wrinkled, worried forehead of a mini-dachshund, but with an overbite. All teeth and neck wrinkles and nearsighted stare: that’s Tuna. Somehow, it’s incredibly cute on a dog.

Dasher first met Tuna at a Los Angeles farmers market in 2010. He was in a local rescue’s booth, and she was on the hunt for a foster friend. “I had moved to L.A. about a year before, and I was living without roommates for the first time,” she says. “I’m an extrovert, I want company, and I told my friend I was a little worried about living alone.” The friend suggested a dog, and since Dasher wasn’t sure about the commitment her pall mentioned that fostering could eb the perfect solution. Help socialize a dog who needs a home, have some company, do a good deed, and then let the pup go to his or her new home when they get adopted. It sounded perfect to Dasher. “I had never heard of that before, fostering. I think it’s more popular today, but back then it felt more common to buy a pet from a store or a breeder. Not that many people understood the importance of rescuing, adopting, or fostering.”

The rescue told Dasher that Tuna had been found on the side of the road in San Diego, and then sat in a county shelter until they pulled him out for foster care. He was only four months old, and so shy that at first he didn’t even walk, he just slunk along in a crouch-crawl. “He looked like a cartoon, like the boss from The Simpsons, so I called him Mr. Burns, but that soon degraded into Toony, like Cartoony, and finally Tuna, which stuck.” As someone who once had a cat named Fangor, who became Fanny, and eventually, Annie, because she just didn’t look like a Fangor, I found Dasher’s story of the name evolution just as relatable as Tuna’s love of naps. Sometimes the animals just name themselves.

As you might have guessed, Tuna quickly became a “foster fail” when the time came to give him up for adoption. Dasher couldn’t imagine living without him. “I formally adopted him on December 26, 2010, and at that point, I had no idea what we would go on to do together. I mean, I didn’t even have a Facebook page. I was the last person you’d expect to get big on social media.” Once again, it was friends who kept nudging her to join this new social platform called Instagram. “My best friend was trying to encourage me to get on. She kept telling me it was very arty, very design-based, and when she showed me what people were posting, I thought, ‘Oh, this is really cool,’ but I didn’t want it to be about me. But I had all these funny pictures of Tuna with his smile. I think the first one was called ‘Daily Tuna Special.’”

Initially, viewers were split between loving Tuna’s goofy charm and posting mean comments calling him ugly and malformed. Dasher realized there was a teaching moment to be had. “I decided I could use this platform to celebrate his unconventional features, and I tried to lovingly point out to people that being mean on the internet is a kind of bullying, and some people came around and apologized, and those that didn’t I would delete and block. It was crazy in the beginning. But now I don’t think I ever get a negative comment about Tuna. And I read every comment every day!”

Tuna was a popular account even in the early days, with thousands of followers back when most accounts only had a few hundred, but what really changed things for Dasher was when the online forum Reddit picked up an image of Tuna. “He was looking off to the side and someone had written ‘thquirrel,’ like a lisp, like he was saying ‘squirrel.’ ” Soon after that, Instagram itself picked Tuna as its weekly pet feature. Overnight, Dasher’s followers went from less than 10,000 to more than 30,000. “I was at a friend’s house when we found out, and we just sat around the phone watching the numbers go up in disbelief.”

Follow Tuna on Instagram: @TunaMeltsMyHeart

As Tuna’s viral popularity grew, so did the opportunities for Dasher. She created calendars and collectibles, took Tuna to meet his fans, and wrote a book about a day in the life of a little dog with a big overbite — and a good-natured acceptance of being dressed up in costumes and bowties. “He’s really a good sport about that,” Dasher says. “I never force him, but he just takes everything in stride, from meeting people to dressing up. Occasionally he won’t be in the mood. I call him ‘Spicy Tuna’ on those days, and I just let him go back to his nap.”

Dasher says she loves getting fan art and hearing from Tuna’s admirers, but even more importantly, she hopes that seeing Tuna’s posts encourages other people to foster and adopt. “Even if you aren’t ready yet, you can donate money or check the wish list for local small rescues. We just want to give back, to bring joy to other people. I feel so grateful to live this life, having my dog as my boss.”

Oh, and one last piece of advice from Tuna: “Don’t neglect your dog’s dental health!” Those smiles are precious and priceless.