By Lynette Rice
Updated November 22, 2011 at 05:01 PM EST

Either folks are starting to head out of town for Thanksgiving or nobody really cares to see Rob Kardashian possibly win the mirror ball: Primetime shows were mostly down across the board on Monday, with Dancing with the Stars posting its lowest performance finale ever.

The episode featuring a dance-off between Kardashian, Ricki Lake and J.R. Martinez posted a 3.6 rating/9 share in adults 18-49, down 27% from last fall’s part 1 finale (4.9/13 on Nov. 22). It averaged 20 million viewers. The action on the dance floor, in turn, delivered a bum rush to the new game show You Deserve It, which earned a 2.1/5 — down 13% from last fall’s Skating With The Stars debut. It averaged 10 mil. Castle, however, was up 13% to a 2.7/7 and lured 11.9 million.

CBS, as usual, won the night in the demo (4.0/10), though it, too, saw across-the-board declines. How I Met Your Mother was down 7% to a 4.3/12 and 10 million viewers, followed by 2 Broke Girls (4.4/11, down 8%, 11.1 million) Two & A Half Men (5.2/13, down 4%, 15.7 million), Mike & Molly (4.2/10, down 5%, 13 million) and Hawaii Five-0 (2.8/7, down 15%, 10.3 million).

ABC finished second in the demo for the night with a 2.8/7, followed by Fox (2.3/7), which saw Terra Nova drop 9% to a 2.1/6 and 6.4 million. House was flat with a 2.5/6 and 7.3 million. NBC’s The Sing-Off, however, saw some gains: The show posted a 1.4/3, up 8%, and 4.2 million. Rock Center with Brian Williams, however, took a step closer to cancellation by earning a .9/2, down 18% from last week, and 3.6 million.