I don't think I even need to find a reason why Sandra Oh's Christina could come back. It's a day that ends in "y," how's that for a reason!? It seems too good to be true that Oh is listed as being part of the show in 2020, but if this season is Meredith and Pompeo's swan song, she absolutely has to make an appearance. If there's anyone who would appear at Meredith's bedside while she's deathly ill, it's her person!