Apparently everyone decided to stay home and watch TV last night (after spending all weekend at the movies). Just hours after the news of massive viewership for the 2012 Grammys, AMC says Sunday’s return of The Walking Dead drew 8.1 million zombie lovers at 9 p.m., the show’s biggest ratings ever. Even more impressive: 5.4 million of those viewers were under 50, making last night’s hour the most-watched episode of a basic cable drama ever in the demo. The news wasn’t as good for Kevin Smith’s Comic Men: AMC’s first foray into unscripted TV lost 75 percent of its lead-in and averaged a mere 2 million viewers.