Leonardo DiCaprio slipped into a back entrance for the launch of Ian Schrager’s West Hollywood Edition and “did a dance-off with a pal when Q-Tip played,” a spy said.

Paris Hilton waited on line with the crowd. Janelle Monáe performed for guests including Billy Idol (who wouldn’t stop making out with girlfriend China Chow, a spy said), Dylan McDermott, Wilmer Valderrama, Estelle, Diplo, CeeLo, and Rumer and Scout Willis.