'Grey's Anatomy' And 'Private Practice' Crossover Scoop From The Set (VIDEO)

There's been so much insanity on "Private Practice" this season -- not the least of which revolved around Cooper (Paul Adelstein) finding out that he has a son, Mason (Griffin Gluck), from a one-night stand he had eight years ago with Erica (A.J. Langer). The new members of their family have tested Cooper and Charlotte's (KaDee Strickland) relationship, but just when everyone was getting on the same page, they found out that Erica has a life-threatening illness that will require a very special surgery.

Who you gonna call? While there are plenty of great doctors at Oceanside Wellness, creator Shonda Rhimes loves any good reason to do a crossover with her other hit show, "Grey's Anatomy." This one brings Amelia (Caterina Scorsone) to Seattle Grace to scrub in with her brother Derek (Patrick Dempsey) and his new right-hand neuro lady Lexie (Chyler Leigh).

They've got a near-impossible surgery ahead of them to save Erica. Will she make it? Or will she die and leave Cooper and Charlotte to raise Mason?

I caught up with the "Private Practice" stars on set to find out if Cooper and Charlotte are ready to be parents, if Amelia's ready to have the stress of a major surgery weighing on her and what it's like crossing over into "Grey's" territory. Watch the video interviews to see what they said, and to find out why someone's pitching a "Doogie Howser"-style twist.