In the aftermath of the Snow Queen's spell, portals were opened up all over Storybrooke bringing in people from realms far and wide - across all universes (even the alternate ones). In a desperate attempt to protect the world at large from the influx of these newcomers, Regina sealed off Storybrooke permanently, making it impossible for anyone to leave the magical town.
So, I can't believe it. But my girlfriend and I are engaged. I always knew it would happen one day. Kimberly is the best thing that ever happened to me.