Hollis became a household name when Nathan picked Callie up from preschool for a doctor’s appointment. As he wheeled her out of the classroom, he noticed someone trailing behind them.

When he turned around he saw a little girl following them to the door. “Hollis you can’t leave with Callie,” one of the teachers said.

When we asked Callie who Hollis was, she replied, “My best girl.”

We’ve always been concerned about how other children would treat Callie. Not just rejecting her, but seeing her as someone to pity. And children have always been nice to Callie — bringing her toys and books — but there’s something special about Hollis.

As with most best friends, it’s nothing we can pinpoint. It’s simply a comfortable presence. It doesn’t matter that Callie can’t sit on the floor to play, dance to the classroom music or chase Hollis around the playground. She simply loves Callie. And Callie loves her.

Nathan and Callie went to Hollis’ third birthday party earlier this month at a gym full of inflatable jumping contraptions. Had it been anyone else’s birthday, Nathan probably wouldn’t have taken her. At that time, we were too caught up in our own sadness, which we projected onto Callie, thinking she would feel bad too.

Instead, Callie had the time of her life. Nathan helped Callie “jump” on every piece of equipment, and he came home with a half-broken back and an ecstatic Callie. Hollis’ mom snapped this picture of Nathan taking Callie down a huge inflatable slide. I understand it was quite a sight watching Nathan hurl himself up the slide holding Callie in one arm and using the other to grasp the toddler-sized climbing ropes.

We’re frequently told how Callie has changed people’s lives. Hollis has changed ours.