When Amy McPherson walks into Shari Nastri’s Jazzercise studio, an hour flies by. “I don’t realize I’m exercising,” she said. “You can come in at any fitness level and be accepted.

The Comme des Garçons Shirt show began, as usual, a couple of minutes before its advertised start time of 9:15am. That so many people wake at the crack of dawn on a Saturday to schlep to Place ...