Credit: Andrew MacPherson/ABC Television Group © 2011 Disney Photo: #9: Addison Montgomery, Grey's Anatomy/Private Practice

Every once in a while, Kate Walsh (Addison Montgomery) comes back to Grey's Anatomy for a Grey's/Private Practice crossover. Every Grey's fan knows this, and most of us look forward to it. Throwing Addison into the Grey's mix always stirs things up.

So when Kate tweeted today, "Gotta go shower in ye olde trailer...did I mention I'm shooting over @ Greys Anatomy today? Oh yeah, it's a goodie too," we started to gear up for another drama-filled crossover.

But then Shonda Rhimes dashed our hopes, tweeting, "Yes, @katewalsh told you all she was filming at Grey's today. That doesn't mean it's a crossover, tweeples," and then confirming that while there might be a crossover at some point, "@katewalsh filming at Grey's today is NOT the crossover."

So what is it? A flashback maybe? No, not that either — when a Twitter fan asked if Kate's filming was a sign that we might "be back in time," Shonda replied "No."

Okay. It's not a flashback, and it's not a crossover episode? We're confused. Does Addison show up at Seattle Grace on Private Practice without interacting with any of the Grey's character?

We suppose in Shondaland, anything's possible.

Update: It's an alternate reality episode! Read more here.

Source: Kate Walsh's Twitter, Shoda Rhimes’ Twitter

Want more from Wetpaint Entertainment? Keep up on all things Grey’s Anatomy by “liking” us on Facebook at facebook.com/GreysAnatomyFansite and following us on Twitter at twitter.com/GreysWetpaint.