Hunter Greene opens the door in his underwear—and only his underwear. It is 5:45 a.m., but he happily offers me a glass of water and welcomes me into his family’s two-story home in Stevenson Ranch, California, with a 360-degree view of the Santa Susanas and, just south of the mountaintops, the city that breeds stars. There are African masks and sculptures all over, arcade versions of Ms. Pac-Man and Centipede upstairs, and a painting of Jackie Robinson in the dining room. On top of the kitchen cabinet, a sign: BE YOURSELF. EVERYONE ELSE IS TAKEN.