In one of her famous novels, Wishfully Drinking, the actress recalled a hilarious anecdote with her Star Wars director, George Lucas, who she joked "ruined" her life.
"George comes up to me the first day of filming and he takes one look at the dress and says, 'You can't wear a bra under that dress.' So, I say, 'Okay, I'll bite. Why?' And he says, 'Because. . . there's no underwear in space.'"
Of course the question remains: But why can't you wear underwear in space (and why can you wear gold bikinis instead)?