Curious what goes on at some of the city's most sought after birthday party places? We were too! That's why we went behind-the-scenes at five of New York City's most popular (and talked about!) spots to host children's birthday parties—places like the new Red Carpet Kids on the Upper East Side and Intrepid Sea, Air & Space Museum, a perennial favorite. A big thanks to the youngsters—ranging in age from six to ten—who invited us to their bashes and showed us just how much city kids love to party.