About four years ago, after acquiring a kitten for one of her daughters, Congdon realized how precious the little critters were.

“When we took the kitten to the vet to get spayed, I mentioned it was so cute, I wished I could always have a kitten in the house,” Congdon said.

Her vet, who is not a wizard, said, “You know, there’s a way you can.”

Without the use of any Harry Potter magic, Congdon was let in on the secret to populating her Sammamish home with a never-ending supply of kittens: fostering.

“She told me about Purrfect Pals, a pet shelter up in Arlington,” Congdon said.

After an interview process and meeting certain requirements, Congdon and her husband Mark began fostering kittens for the shelter.

They’d care for baby felines, getting them acclimated to home life, away from the chaos of a shelter.

“It helps them socialize. It gets them used to dogs, doorbells, neighborhood kids coming over and playing with them. By the time they’re old enough, they’re ready for adoption,” Congdon said.

It was difficult at times fostering for Purrfect Pals — located an hour away — especially if the kittens got sick. So she reached out to Seattle Humane and signed up for their fostering program, too.

Little did she realize her obsession with the kittens would go viral on Instagram.

“Once we got them, of course our phones started to fill up with pictures of them,” Congdon said. “So we thought, ‘Wouldn’t this be fun to start up a social media account?’ so people who adopted the kittens could look back at the pictures of them growing up.”

There were no other fostering accounts created at the time, so she co-opted the name “foster_kittens.”

“It has just taken off. It’s shocking how quickly it’s grown,” Congdon said.

When the number of followers blew past 10,000, they knew they had something special on their hands. Today, Congdon’s account is the biggest foster account on Instagram at 423,000 followers.

To be clear, Congdon realizes she doesn’t have the largest overall Instagram account about cats.

“There are bigger cat feature accounts, some with millions of followers, but mine is the first and biggest foster account,” she said.

Armed with her iPhone 7, Congdon will upload new photos of the kittens every couple of hours. Prospective families can then watch the kittens as they grow — see them right from birth, see their eyes open for the first time, watch them navigating the stairs.

“These families really, really feel attached. So when they’re ready to adopt, they’ve watched this kitten be born sometimes and grow up, so these are people who’ve made huge efforts.” Congdon said. “These are not people at PetSmart buying food and saying, ‘Oh, I think I’ll adopt a kitten, too.’ ”

Purrfect Pals places their kittens only to in-state residents. Seattle Humane will adopt them out to anyone, but only if you’re willing to fly in and pick them up.

“We’ve had people fly down from Canada. One flew down from Alaska, another over from Nebraska. We’ve had San Francisco and Texas. Not that there are no cats in Texas — they’ve just seen the cats grow up and grown attached to them and make arrangements to fly out and adopt a kitten,” Congdon said.

She said people from all over the world send the kittens presents, even Christmas cards. “It shows there’s such a common bond over little kittens, no matter who you are or what language you speak,” she said.

“So, like at PetSmart in Sammamish, it would start at 10 a.m. One time they started lining up at 4 a.m. By the time employees opened the door, there was a line around the store.”

So they began collecting applications in advance, picking out the most-qualified families and inviting just those to the adoption events. Often, the shelters would put kittens there from other foster homes on the same day, so if families didn’t get one of Congdon’s little ones, they’d get the opportunity to walk away with another one.

Congdon’s records show they’ve fostered 112 so far, counting current kittens Joey and Max. With that many coming and going, she’s enlisted the whole family.

“My twin teenage daughters, Rebecca and Rachel, they’re very, very involved. These guys (pointing to Max and Joey on the couch with her) showed up covered in fleas. It takes three people to bathe a kitten,” Congdon said.

Often, they foster pregnant cats and occasionally they’ve taken care of kittens that didn’t have a mom. That requires round-the-clock feeding for the first few weeks, by bottle or syringe for the very young ones.

“It’s nice, having them involved. Plus it gives my daughters an excuse to invite their friends over. It’s always a hub of activity here,” she added.

The other thing Congdon tracks is names, never using the same one twice, even if only about 50 percent of the families keep the names she’s given.

“Foster names are temporary. It doesn’t matter anyway — like cats come when you call them,” Congdon said. “But names are important to me. They’re really cute, but if it’s a name like Herkimer, or something really terrible, then people won’t want them. So we always try to give them something cute.”

So far, except for Felix, who was born the day an adult foster cat died, they’ve avoided the temptation to keep foster kittens. Congdon admits it can be hard.

“I cry on adoption day,” she said. “We try to plan a dinner or a soccer game, anything so we can stay busy. But usually we get to meet the family on adoption day. It’s exciting, they’re so happy, it’s a great feeling. Often those people will start their own Instagram account so we can see the cats grow up.”

The trick to fostering kittens, Congdon said, is going in knowing it’s not going to be your cat.

“It’s like you love all your girlfriends or boyfriends, but you only want to marry one,” she said. “I love them, but I don’t want to adopt all of them.”

Follow Sammamish resident Cindy Congdon’s popular Instagram account at instagram.com/foster_kittens.