Season 4: Ava/Rebecca Pope
Rebecca Pope (Elizabeth Reaser) first pops up in the third season as Alex's pregnant Jane Doe patient. However, she plays a more prominent role in the fourth season when she and Alex start a fraught relationship. Her character brings out a sweeter and more vulnerable side to Alex, though they share a fairly dysfunctional experience together. Eventually, heeding Izzie's advice, Alex agrees to have Rebecca checked out by the psych department.