Tonight, the Grey's Anatomy-Private Practice crossover event concludes with "An Honest Mistake." Tensions are running high between Derek and Addison - and Derek and Mark.

Elsewhere at Seattle Grace this evening, Izzie Stevens learns her test results were mixed up, Callie asks Arizona out on a date, a veteran surgeon botches a relatively standard procedure, and Dr. Bailey is shocked by the Chief's recommendation letter.

Check out the videos and photos we've posted for more info!

As always, you can discuss "An Honest Mistake" before, during and after the episode in our

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