Jeffrey Ufberg/WireImage

WHAT SHE WORE A fitted Zac Posen sheath, Irit diamond earrings and black patent Sergio Rossi pumps

WHERE Outside the Late Show studios in New York City

WHY WE LOVE IT Willis channeled Mad Men-era sex appeal in a sophisticated little white dress with cutouts at the shoulders. If you don't have Rumer's perfect figure, choose a design with an empire waist and fuller skirt—you'll still get all the benefits of playing peekaboo without feeling on display.
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Rumer Willis

Rumer Willis in Zac Posen