Gained 20 lbs (9 kg; 1 st 6 lb) for the part of Kaylee in the TV series Firefly (2002). When the show was later adapted into a motion picture (Serenity (2005)), the show had been over for a little while and she had lost the weight. She was told that they weren't going to give anyone else the part anyway, so she didn't have to re-gain the weight.
