What are your favorite Philadelphia stories, legends, fun facts?

What do you tell tourists, out of towners, and new arrivals?

For example, I just yesterday learned City Hall's Billy Penn statue faces northeast because developers who owned in that direction wanted to make sure the new residents would know they were part of philly.

Also, the worlds largest Calder mobile hangs in the Federal Reserve building.

And Christ Church at 2nd and Market was, for more than a few years, the tallest building in North America.

What are your favorites? The more obscure, the better, particularly if not well known fact with implications that ripple to the current day.