Kourtney Kardashian, Ashlee Simpson
Credit: Michael Buckner/Getty Images

Kourtney Kardashian and Ashlee Simpson headed to Hollywood to kick off Caesars Entertainment's "Escape to Total Rewards," a series ofsimultaneous concert events in four cities. "Im Escaping w/ @Total Rewards Lil Wayne & @CeeLoGreen tonite @ Hollywood & Highland!" Kardashian tweeted. Click through the gallery to see Jennifer Lopez, Salma Hayek and more stars at last night's hottest events.