The universe isn't actually a universe at all - it's a multiverse. Millions upon millions of parallel worlds exist simultaneously, and time means nothing. Time is a linear construct imposed by man to make sense of his own particular world.
Sometimes, the walls between these multiverses thin. Thoughts and ideas from one universe can bleed in to another, leading to a rise in fantastical stories and ideas.
And sometimes, the walls disappear. There's no sign that it has happened, except that you might be walking down the street, turn a corner, and find yourself in another universe. Perhaps even another time.
It's just happened in New York City.
It may look the same. It may even sound the same. But believe me, this is not your New York. You're just going to have to survive the best you can.
This is a roleplaying community, positing that characters from alternative universes (any fandom) are appearing in a version of New York City, circa 2007. Applications are welcome from any fandom, as are original characters.