Her pooch "Gatsby hated [the new dog]," the actress tells PEOPLEPets.com

Actress Autumn Reeser was all smiles on Easter when she adopted a 3-month-old mutt named Sadie who had been abandoned at L.A.’s Griffith Park. But the grins faded once her other dog Gatsby reacted bitterly, refusing to get along with the new pup.

“Gatsby hated her–for a straight week,” the Entourage star tells PEOPLEPets.com. “He wouldn’t come to bed, he wouldn’t do anything. He was like, ‘I’m over you guys. I know what’s happening, I know what you’re doing, and I don’t like it.’ “

But Gatsby finally came around, and the two canines can now seemingly not get enough of each other. “They started playing because they were the same size,” Reeser explains. “And now, every morning for an hour, and every afternoon for an hour, they chase each other. It’s like a light goes on in their head and they think, ‘Okay, time to wrestle.’ “

The cuteness doesn’t stop there. “My favorite thing about Sadie is she walks Gatsby,” Reeser says. “If we put his leash on first and just leave him running around, she walks him over to us.”