Private Practice Spoilers: Derek's Past

Entertainment Weekly's Michael Ausiello has a brief tidbit on the upcoming Private Practice / Grey's Anatomy crossover event in his spoiler Q&A today - specifically, Addison & Co. shaking things up. Here's what he says is on tap:

Q: What is the cast of Private Practice going to do at Grey's Anatomy?

A: Filling Meredith's pretty little head with shocking stories about Derek's early days ** * **********. And believe me, that's not a good thing. Funny? Yes. Good? No.

Can you fill in the blanks? We know Addison, her brother Archer, and perhaps even Sam and Naomi (from medical school) share a history with Derek. What do you think will be revealed - and how will it play out?