Big Brother, the underappreciated Energizer bunny of network reality shows, continues to retain an iron grip on its loyal viewership. Last night's thirteenth season premiere averaged nearly 8 million viewers and earned a 2.7 rating with voyeurs aged 18 to 49. That made it the top show of the night in the key demo, handily outdrawing Fox's 8 p.m. installment of So You Think You Can Dance and ABC's 9 p.m. newcomer Expedition Impossible. If preliminary numbers hold up, it'll be the show's best debut since 2007; one reason for the upward bump is that CBS wisely moved the Thursday show into a 9 p.m. time slot rather than the lower-viewed 8 p.m. leadoff position. Meanwhile — and this is a big-time spoiler for those Big Brother fans who don't monitor the live feeds — the Internets are saying that contestant Evil Dick appears to have left the game. A CBS rep didn't immediately respond to a request for comment.