Who said that two people need to be the same sex to look alike? We even think that when Alex Newell was playing Unique on 'Glee' (aren't there a lot of Glee alumni on this list?), he was actually deliberately channeling Chandra Wilson in places. He's never said so himself; he cites Beyoncé, Aretha Franklin, Diana Ross and Chaka Khan as his primary influences, but at times the performance was so reminiscent that there's no way he didn't have her in mind.
Wilson is one of the stalwarts of 'Grey's Anatomy', having been in the show since 2005, and showing no signs of giving her role up any time soon. If anybody needs to play her younger self in flashback scenes; or there's call for a story involving a relative of her turning up in her life, they could do a lot worse than give Newell a call.