Season 2 of Ricky Gervais's show about a struggling actor keeps its central gag: Stars from David Bowie to Harry Potter's Daniel Radcliffe play themselves, usually as egomaniacal jerks. But Gervais tweaked the story. His character, Andy Millman, launches a sitcom, a sellout piece of working-class schlock called When the Whistle Blows. Andy's humiliations as a minor celebrity aren't quite as funny as was his earlier shame at being a nobody, but as a satire of showbiz vanity, Extras can still be described as (what else?) stellar.