New Grey's Anatomy-Private Practice Crossover Previews

Below is the latest preview of the much-anticipated Grey's Anatomy-Private Practice crossover event, in which the worlds of Shonda Rhimes collide on Thursday night.

Here's what happens in L.A. between Private Practice's Addison and her brother, Archer, that prompts her to seek help from Derek, her famous Grey's Anatomy ex ...

For another sneak preview - this time from the Seattle Grace side of things - follow the jump. Then follow this link for the latest Private Practice and Grey's Anatomy spoilers!