Critic's corner

The Truth About Cancer
9 p.m., Channel 2
This 90-minute documentary, followed by a panel discussion, tries to dispel the "Lance Armstrong" myth that all it takes to fight cancer is inner strength and a positive attitude. That's not especially hopeful, but it's honest.

9 p.m., Channel 56
Meet the wimpiest contestants on reality TV. Maybe they're just scared of Robin Antin. I know I am, a little.

8:30 p.m., Channel 25
The Kelsey Grammer-Patricia Heaton sitcom returns with the first of five new episodes. The laugh track is back in action!

10 p.m., MTV
Seven strangers. A house in West Hollywood. A guy chosen by viewers who calls other people "peasants." MTV's once-groundbreaking reality show, which premieres its 20th season tonight, proves one thing: In all these years, twentysomethings haven't gotten any wiser.

8 p.m., Channel 5
Clinton and Obama face off in Philadelphia. Otherwise known as "Moment of Truth."

10 p.m., Bravo
Their attempt at block party food was a near-disaster. Now, the chefs try to tackle a tailgate. Please, guys, no paella.

10 p.m., Comedy Central
Still not for the faint of heart, and still as funny as ever.

Comcast, Encore
It plays like an entire movie studio dropped on your head. Aliens in massive flying saucers aim to clobber us, and President Bill Pullman must lead the resistance, which includes scientist Jeff Goldblum and fighter pilot Will Smith. Imagine Cecil B. DeMille directing "War of the Worlds" and you've got the picture. (PG-13; runs through April 24)