Eilish also channelled Old Hollywood for the evening, with her shaggy blonde bob styled in Marilyn Monroe-esque waves and her makeup kept classic with her eyes rimmed in black liner and her lips painted a rosy nude (makeup artist Rob Rumsey used Charlotte Tilbury K.I.S.S.I.N.G. Lipstick in Runway Royalty over the brand's Lip Cheat in Iconic Nude).