Scant weeks after the conclusion of the last installment, “The Biggest Loser” (7 p.m., NBC) returns with a new wrinkle. This time, the teams consist of couples trying to shed pounds by the hundreds and competing together against other couples, too.

With few exceptions, game shows and reality series that resort to gimmicks tend to be on the downward slide. “Survivor” was getting a tad tired when it invited “all stars” to compete. On the other hand, the dynamics between bickering married couples, engaged lovers and teamed-up family members has worked for “The Amazing Race,” so it could work here.

But will the couple casting work with the show’s hardcore audience? Will the folks who have rooted for individuals care about couples? Just who is still watching this show?

¢ Ever wish you could “test-drive” a prospective new house? With the real-estate market in a challenging mode, perhaps that’s not such a radical idea. This is the gist of the new series “Sleep on It” (9 p.m., HGTV), which invites potential buyers to spend the night in their favorite on-sale property.

But just how will the would-be buyers feel after spending the night? Will they hate themselves in the morning? Will they lose all respect for the house that once left them smitten? Will they rush out without so much as a goodbye as a desperate seller silently mouths the words “call me”?

We’re assured that some suitors do stick around for breakfast and even make an offer to make an honest broker of their one-night stand.

¢ Happy New Year. Remember to write “2008” on all your new checks and correspondence. And you also have to keep up with the changing names of cable channels.

Remember Court TV? That’s so 2007. It’s now truTV, home to “Ocean Force: Huntington Beach OC” (7 p.m. and 7:30 p.m.), a documentary variation on the “Baywatch” theme, with shapely lifeguards in orange bathing suits rescuing swimmers and surfers and swept-away sand-castle makers in the warm California sun.

This month, Discovery Times will become Investigation Discovery. This name change (I hate the word “rebranding,” don’t you?) reflects the fact that The New York Times, once a part owner of the network, has sold its interest and is no longer affiliated.

¢ Walter Cronkite hosts a “Great Performances” (7 p.m., PBS, check local listings) tradition: “From Vienna: The New Year’s Celebration 2008,” featuring the Vienna Philharmonic under conductor Georges Pretre. Some PBS stations will also broadcast this at 1:30 p.m.

Tonight’s other highlights

¢ Illinois and USC clash in the Rose Bowl (4 p.m., ABC).

¢ Georgia and Hawaii battle in the Sugar Bowl (7 p.m., Eastern, Fox).

¢ The squad has to choose between rescuing a former dictator or 10 of its wounded victims on “The Unit” (8 p.m., CBS).

¢ Scheduled on “48 Hours Mystery” (9 p.m., CBS): Just what motivated a wife to stab her husband 193 times?

¢ A wealthy teen’s murder gets pinned on a gang of homeless kids on “Law & Order: Special Victims Unit” (9 p.m., NBC).

¢ Murder most fowl on “Boston Legal” (9 p.m., ABC).

Cult choice

In the 40-plus years after the tragic end to Camelot, the Kennedy-family saga has inspired dozens of TV movies and miniseries. Apparently, the genre came to an ignominious end with the 2003 effort “America’s Prince: The John F. Kennedy Jr. Story” (8 p.m., Lifetime). At the time, I was inspired to write, “Just when you think ‘Prince’ can’t get any more tasteless, another scene unfolds that leaves you gasping.” Now that’s my kind of movie!