Sunday's first-season finale of Dexter drew an audience of 1.1 million total viewers, a 79 percent increase from the Oct. 1 series premiere, and Showtime's most-watched original-series episode since Nielsen started crunching the cabler's numbers. It also ranked as Showtime's most-viewed program of 2006.... ABC Family's "25 Days of Christmas" effort, fueled on Sunday by the premiere of Christmas Do-Over (2.7 million viewers) and a visit from the Grinch (3.5 million), led the network to double-digit gains versus a year ago.... Toby Keith's acting debut, Friday's Broken Bridges (1.4 million viewers), ranked among CMT's most-watched original telecasts ever.