When Michelle Calicchio and her family adopted a yellow lab named Maggie in 2005, they thought she'd be their only dog for a while. Little did they know that over the next 12 years, they'd foster over 60 dogs β€” and those foster dogs would connect with Maggie in an unusual way.

It all started several years ago, when Calicchio took temporary ownership of a tiny stray Chihuahua named Percy, whom Calicchio's found wandering around an Arizona neighborhood. Eventually, Percy had to go back to his original owner, but Calicchio was hooked after that. So, she decided to start fostering Chihuahuas and other small dogs with AZ Happy Tails Animal Rescue.

Yellow lab who allows chihuahua to sleep on top of herMichelle Calicchio

Today, Maggie, Calicchio's big yellow lab, lets the foster dogs snuggle up to her. One day, one of the foster dogs, named Jasper, hopped onto Maggie's back and laid down β€” right on top of her.

Yellow lab who allows chihuahua to sleep on top of herMichelle Calicchio

"We just thought that is so odd," Calicchio said. "We thought, 'Why is he doing that?'"

Yellow lab who allows chihuahua to sleep on top of herMichelle Calicchio

But Jasper wasn't the only one. Calicchio said that about 25 of the dogs she's fostered have used Maggie as their personal dog bed.

Yellow lab who allows chihuahua to sleep on top of herMichelle Calicchio

"She just lies there and allows it," Calicchio said. "She's not super interactive with them. She doesn't necessarily seek them out, but they seek her out."

Yellow lab who allows chihuahua to sleep on top of herMichelle Calicchio

"I think it's because she's warm and she's soft," Calicchio added. "But it's the strangest thing. Not every single one of them does it, but a lot of them do, and independently of each other β€” so it's not a learned behavior. I don't know what it is about her."

Yellow lab who allows chihuahua to sleep on top of herMichelle Calicchio

Dr. Jill Sackman, senior clinician and animal behaviorist at BluePearl Veterinary Clinic in Michigan, has an explanation to offer.

Yellow lab who allows chihuahua to sleep on top of herMichelle Calicchio

"She must be a very sweet dog who enjoys companionship," Sackman told The Dodo. "I think there are a lot of labs out there who are like this, and who enjoy the company of other dogs. The foster dogs might be nervous and insecure, and she allows them to touch and snuggle with her."

Yellow lab who allows chihuahua to sleep on top of herMichelle Calicchio

Whatever the reason, the foster dogs certainly make themselves at home on top of Maggie.

Yellow lab who allows chihuahua to sleep on top of herMichelle Calicchio

"I actually have pictures of dogs who have taken bones, and they will climb on top of her and chew their bones, and she just lays there," Calicchio said. "Every time it happens, we think it's so unique!"

Yellow lab who allows chihuahua to sleep on top of herMichelle Calicchio

"It's almost like she doesn't even notice, because if she hears the treats bag, and there's a dog on top of her, she'll just get up and they'll go tumbling off," Calicchio added. "It's crazy."

Yellow lab who allows chihuahua to sleep on top of herMichelle Calicchio

And Maggie doesn't seem to mind.

"Maggie has got to be the world's most tolerant dog," Calicchio said. "She's also very mellow and very calm and quiet. I've never seen her not let one of them cuddle her.