The other day, I was on a local 6 going uptown and seated next to a young woman with a baby in a stroller. At each stop, a man (always a man) would enter the car and end up standing right above us. I had my iPod on and was just watching. Inevitably, each man would make goofy faces and smile at the baby, and the baby would smile and make faces back. At each stop, the standing man would be replaced by a new one, straight out of central casting: First, an older Latin guy. Then he gets off and a young black man appears. Then a white man in a suit. Then a construction worker with a hard hat. Tough guys. New York guys. All devoted to one important task: making a baby smile.