TV Guide reports this morning that Grey's Anatomy and its spin-off, Private Practice, will be embarking on a multi-episode crossover story for February sweeps.

Though at this very early stage the number of episodes and the sum total of actors involved has yet to be nailed down, it can at least be confirmed that Kate Walsh's character, Dr. Addison Montgomery will again be walking the halls of Seattle Grace.

Addison returned for one episode late in Season Four after leaving the Grey's Anatomy cast for the sunny skies of L.A. and Private Practice after Season Three.

What brings Addison (Kate Walsh) back to Seattle this time?

Who from Seattle Grace might show their face at Oceanside Wellness? Walsh personally cast her vote for Mark Sloan, saying, "It'd be fun to have him cause some trouble!"

That said, the actual list of involved cast members from each show, besides Walsh, is unconfirmed. Who would you like to see - and under what premise?

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.