It was an unlikely pairing, to be sure. But eight-month-old Mini Rex rabbit Shakira is the best thing to happen to Mack, a two-year-old bulldog-boxer mix. Soon after Midtown’s Nick and Rosa Arnold adopted Mack from the Atlanta Pet Rescue last April, it became apparent that the whip-smart dog was something of an escape artist. While they were at work, he would open doors, eventually mastering the dead-bolted front door. The Arnolds, thinking they were clever, tied the front door shut. So Mack showed them. He jumped through the window! Then, after that, two more. Rosa, who had a bunny as a child, convinced Nick that a cotton-tailed companion was in order. “At first it looked like he wanted to eat the bunny,” says Nick. But now the two are “best buds.” Mack and a leashed Shakira especially love to go on walks (and, in her case, eat grass) in Piedmont Park.