Today on TV

NFL football (6:30 p.m., ESPN): Vikings at Packers

How I Met your Mother (7 p.m., Ch. 2): Robin and Barney keep a secret from their significant others

Dancing With the Stars (7 p.m., Ch. 4): The competition continues.

The Sing-off (7 p.m., Ch. 5): The top 5 acts, including Utah's Vocal Point, perform.

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Terra Nova (7 p.m., Ch. 13): Maddy learns a secret that puts her life at risk.

Two and a Half Men (8 p.m., Ch. 2): Alan is faced with challenges that test his mental stability.

House (8 p.m., Ch. 13): House tries to remove his ankle monitor.

Hawaii Five-0 (9 p.m., Ch. 2): The physically altered corpse of an unidentified man is found in the trunk of a stolen car.

20/20 (9 p.m., Ch. 4): Gabby and Mark: Courage and Hope

Rock Center With Brian Williams (9 p.m., Ch. 5): Sportscaster Bob Costas discusses the sex scandal surrounding a former Penn State football coach.