Looking for a couple's costume? Be royalty for the night and dress as style icon Kate Middleton and her husband, Prince William. For Kate, pair a short-sleeved, polka-dot dress in a simple, flattering cut with classic pumps in cream or nude. For William, wear a dress shirt in a hue that compliments Kate’s dress, dark corduroy pants, a brown belt and a watch. If you’re committed to going all-out, wrap a baby doll in a white blanket to represent little Prince George.