Duel

(8-9:30 p.m., 6ABC) - No slaps with a glove, pistols at 10 paces or psychotic truckers in this

Duel

. It's a six-episode game show in which 20 players compete one-on-one with one another in a series of trivia challenges. When four are left standing, a final showdown will determine the winner of the jackpot, which could be $1.5 million or more. The host is Mike Greenberg of radio's

Mike and Mike in the Morning

.

Clash of the Choirs

(8-10 p.m., NBC10) - Why should vocal soloists and bands have all the fun? This new reality series pits five amateur vocal ensembles against one another for the title of America's best choir - to be determined by viewer votes. Celebrity choirmasters Patti LaBelle (heading the Philadelphia entry), Michael Bolton, Blake Shelton, Nick Lachey and Kelly Rowland choose the members from residents of their respective hometowns and prepare them for the competition.

Aliens in America

(8:30-9 p.m., CW57) - Raja (Adhir Kalyan) announces his warm feelings toward his new friend, Justin (Dan Byrd), in front of the whole class. If Justin thought he'd been picked on before, he hasn't seen anything yet; now the whole school is calling him Raja's boyfriend. On Claire's (Lindsey Shaw) advice, he starts ignoring Raja - who befriends another kid, leaving Justin lonelier than ever.

Great Performances

(9-11:30 p.m., WHYY TV12) - Mahagonny, Mahagonny, that toddlin' town . . .. An opera for people who think they don't like opera, Kurt Weill and Bertolt Brecht's

Rise and Fall of the City of Mahagonny

is a satirical tale of a town that was built for pleasure but not immune to pain. Audra McDonald, Patti LuPone, John Doyle (

Sweeney Todd

) and Anthony Dean Griffey star in this new production by the L.A. Opera.

Two and a Half Men

(9:30-10 p.m., CBS3) - Is there a new stepfather in Charlie and Alan's (Charlie Sheen, Jon Cryer) future? If so, they could do worse than Evelyn's (Holland Taylor) latest love, Teddy (guest star Robert Wagner), who has his own jet and offers the brothers a trip to Las Vegas. A fun time, for sure, but it does open some old daddy-related baggage for them

.