The last lead to be cast was Leia. “I had another girl who was much younger, who looked like what you might envision as a princess [Terri Nunn],” Lucas says. “She was very pretty and petite, but she also had an edge to her. Whereas Carrie is a very warm person; she’s a fun-loving, goofy kid who can also play a very hard, sophisticated, tough leader. This other girl couldn’t play sweet and goofy. Whereas with Carrie, if she played a tough person, somehow underneath it you knew that she really had a warm heart. So I cast it that way. The princess is one of the main characters, so the actress was going to have to be able to generate a lot of strength very quickly with limited resources available—and I thought Carrie could do it.”

-from The Making Of Star Wars by J.W. Rinzler