'Perfect Couples' gets an early preview after 'The Sing-Off' [Updated]

UPDATE 12/17: NBC has rethought its scheduling a little bit. "The Sing-Off" finale will stay at two hours, and the "Perfect Couples" preview will air at 10 p.m. Monday. An "Office" repeat will air at 10:30.

The original post is below.

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NBC is expanding the season finale of "The Sing-Off" by a half-hour -- and hoping you stick around for a preview of one of its new shows after that.

The network will air an episode of its new comedy "Perfect Couples" at 10:30 p.m. ET on Monday (Dec. 20), following the crowning of the "Sing-Off" champion. The show will become part of NBC's all-comedy lineup on Thursdays starting in January.

"The Sing-Off" has performed solidly in its December run this year, averaging about 8.5 million viewers per episode and a 2.9 rating in the adults 18-49 demographic. Both figures are significantly higher than those of "Community," which will be the lead-in for "Perfect Couples" come Jan. 20.

The "Perfect Couples" episode NBC is airing Monday won't be the series pilot, so let us get the exposition out of the way for you now. The show is about three couples in three different kinds of relationships: Julia (Christine Woods, "FlashForward") and Dave (Kyle Bornheimer, "Romantically Challenged") are relatively stable and sane; Dave's best friend Vance (David Walton, "100 Questions") is in a hot-and-cold relationship with Amy (Mary Elizabeth Ellis, "It's Always Sunny in Philadelphia"); and they're all friends with Leigh (Olivia Munn) and Rex (Hayes MacArthur, "Worst Week"), who fancy themselves as relationship experts.

Monday's episode will find Dave and Julia trying to glam it up on date night, Amy and Vance dealing with bedbugs and Rex and Leigh struggling to adjust to the time difference while on vacation.