The best outfit of the 2000s, hands down.
What you need to do: Denim on denim is the way to go here. To be Britney, wear a denim dress or a denim shirt with a denim skirt. Find a sparkly necklace, and add a long blond wig. To be Justin, wear light-wash denim jeans with a denim shirt and jacket. Then, find a denim cowboy hat and throw on some brown shades.