Emilie de Ravin
Was: Claire Littleton, the pregnant Australian who was kidnapped by the Others in an attempt to study what happened to a woman who conceived off the island. She gave birth to her son, Aaaron, on the island in Season 1. She became mentally unstable after Kate took him off the island as part of the Oceanic Six, claiming him as her child. When the group returned without Aaron, Claire attempted to kill Kate.
Is: Guest-starring on ABC's Once Upon a Time, which is the brainchild of former Lost writer/producers Adam Horowitz and Edward Kitsis. Once revolves around about a small town in Maine where life is a fairy tale (and that’s not always a good thing).
Lost flashback quotient: De Ravin is playing playing the roles of a mental patient and Belle from Beauty and the Beast. If she starts talking about her "friend" or playing with knives (or cuddling squirrel babies), we may have cause to worry.