Reese Witherspoon's Water for Elephants Dress
Jacqueline West, David James/ Twentieth Century Fox

To play a circus performer in the big-screen adaptation of Water for Elephants, Reese Witherspoon had to transform her chic modern style into a believable retro look, something she couldn’t have done without the expertise of wardrobe designer Jacqueline West.”In the 1930s, gowns were very revealing, ” says West. “The women of that era wore them without any underwear, so that’s what Reese did. She was very brave.” Witherspoon’s co-star Robert Pattinson also got into character with his unmentionables. “He loved that I had authentic 1930s underwear for him,” West remembers. “He said it helped transport him.” Click through to see West’s sketches of the pair’s most memorable looks.

BONUS! Win a one-of-a-kind reproduction of the red gown Witherspoon’s character wears! How to win the dress shown: Visit the InStyle Facebook page this Friday, April 22nd (the same day the movie hits theaters) at 3pm EST and be the first person to correctly answer a trivia question.