Which Reese Witherspoon Monsters vs. Aliens Look Is Most Fab? Reese Witherspoon has temporarily traded her jeans for pretty frocks to promote her latest 3-D flick, Monsters vs. Aliens. From Berlin to London to Madrid, the smiley actress mostly opted for knee-length dresses by the likes of Prada and Valentino. All of her choices are very Reese — ladylike, chic — but which look is most Fab?