When Leighton Meester steps onto the red carpet, she's a fashion force to be reckoned with. The Gossip Girl's ensembles get more and more refined with each event. Sometimes she's super sexy, others ultra femme, and from time to time a full-on movie star in floor-grazing gowns. She's constantly switching it up, that's why she's refreshing to follow. But such was not always the case. When Leighton first hit the red carpet in 2003, her uniform of choice was jeans and fancy tops. A lot has changed since then, including her hair color. Take a trip down memory lane to see Leighton's impressive fashion metamorphosis.