When there's no dress code on the invite, guests are free to interpret the "party dress" with their own brand of styling. Such was the case at last night's iHeartRadio 20/20 Justin Timberlake album release party, where attendees like Nikki Reed, Jordin Sparks, and Emmy Rossum celebrated JT with their own take on eventwear. Nikki made a case for the classics, keeping it easy in skinny pants and a semisheer button-up, while Jordin worked a cool-girl angle in leather pants, sexy heels, and a moto-style jacket. As for Emmy, she adopted a more ladylike approach, arriving in a sweet floral-embellished Topshop sheath and white heels. For the rest of the party guests, just keep clicking — then be sure to cast your vote for the night's best dressed.