You meet all types on the street, often by accident: dog walkers, transvestites, women with triplets, men in clown suits, veterans, gangs.
There are teachers, students, people from every country imaginable. People walk with their dogs, their cats, their parrots, their musical instruments. It's a little like The Breakfast Club.
There are commoners and there are celebrities, too. Like Jackie Onassis.
The graphic artist Chris Ware created a lovely animation for This American Life on just such a situation: running into a celebrity on the streets of New York.
Related posts: The Sublime and Ridiculous, Or Why I See Few Celebrities in New York and A Bit More on Celebrity, Past and Present