"Hi, Katie," Calvin said, his smile coming easily at the sight of her, returning informality for formality and stepping right in like he hadn't even noticed that it had been pretty much forever since he'd been to her house. "How are you doing today? That's a pretty skirt." He hadn't thought to dress up; he looked nice (his mother wouldn't let him out of the house if he didn't so it was ingrained) but not in the least formal.
He continued into the house and toward her room -- after all, he knew where it was, and he assumed that's where they'd be going. Full speed ahead.