From “Out of Character” by Joan Acocella, a profile of Frances McDormand in the March 3, 2003 issue of the New Yorker:
Again there is a note of perversity mixed in with the modesty. Concerned that she was too small-breasted for certain roles, McDormand got herself a pair of prosthetic breasts -- "lovely, big, C-cup, jiggly things" -- which she would haul around with her, in a box, to auditions. (She wore them in "Fargo," because her character was pregnant, and on that subzero set one of them froze and exploded. "I advise women with silicone breasts who are going to Minnesota not to stand outside in the cold," she told W.)