Rihanna, Cara Delevingne smolder at the 'Valerian' premiere

When you're Rihanna, you always opt for the unexpected.

At Monday night's Los Angeles premiere of the sci-fi epic, Valerian and the City of a Thousand Planets, in which Rihanna stars as a sexy, shapeshifting alien named Bubble, the pop star went backward in time, opting for a bubblegum pink, Victorian-inspired frock, complete with lace-up heels.

Co-star Cara Delevingne stayed more on theme, pairing a sheer, futuristic silver dress with a glam hairstyle that invoked Old Hollywood finger waves. 

In Valerian, Delevingne stars as a cosmic operative who goes undercover in an attempt to save Alpha, an idyllic city housing 1,000 planets and alien species, from an unknown threat. 

A sizzling space pair? Indeed.

Valerian and the City of a Thousand Planets hits theaters July 21.