Amy Brenneman (Judging Amy) has been cast in the potential Grey's Anatomy spinoff, reports Reuters. Like the rest of the posible new cast, Brenneman will be appearing in the "enhanced" two-hour episode of Grey's that may serve as the backdoor pilot for the new medical series starring Kate Walsh. Already signed to appear in the episode -- and possibly the series, if it gets off the ground -- are Taye Diggs, Tim Daly, Chris Lowell and Paul Adelstein. The episode is tentatively titled "My Favorite Mistake," though whether as a reference to the Sheryl Crow song or to competition medical dramedy Scrubs, we may never know.