TONIGHT'S MUST-SEE

"The Biggest Loser," 7 p.m., NBC. This is "green week" for NBC, with lots of eco-themes. That's hard to work into some shows — chase scenes on fuel-efficient motor scooters? — but easy for a reality show. Tonight, the contestants try recycling. They also learn ways to exercise without electricity. Hey, didn't our ancestors get lots of non-electric exercise?

"The Real Housewives of Orange County" season opener, 8 p.m., Bravo. The bottle-blonde women here often seem interchangeable. Still, real tragedy and joy does intervene. Tammy Knickerbocker's daughters were stunned by the death of their father (Tammy's ex-husband). Vicki Gunvalson's kids are gone to college, but she keeps injecting herself into their lives. Lauri Waring is trying to squeeze a 400-person wedding into her yard. Joining the show is Tamra Barney, 39, a bikini beauty who argues with her son, 21. It could be a busy season.

OF NOTE

"Bones," 7 p.m., Fox. An intern at the institute, the daughter of a scientist, was killed. Is that linked to a case she was working on or to a romance or to something else? Meanwhile, Booth pretends to be the boyfriend of Cam (Tamara Taylor) at a family dinner.

"Carpoolers," 7:30 p.m., ABC. We meet the crazed ex-wife of Laird (Jerry O'Connell). She's played by Rebecca Romijn, O'Connell's real-life wife.

"House," 8 p.m., Fox. Dr. House is supposed to diagnose a CIA agent. That's not easy because the agency doctor (Michael Michele) won't tell him any of the background.

"The Unit," 8 p.m., CBS. Jonas and Williams try battlefield surgery to save Grey's life.

"Nip/Tuck," 8 p.m., FX. There are some good story lines that involve Sean and include superb actresses. He's dating an actress (Paula Marshall); he also gets a big surprise from his ex-wife (Joely). There are also some tacky stories involving jealousy — by Sean and by two Marilyn Monroe look-alikes.

"Law & Order: Special Victims Unit," 9 p.m., NBC. There seems to be a copycat following a famous serial killer. Benson questions a comic-book writer whose work has been glorifying the killer.

"Boston Legal," 9:02 p.m., ABC. Alan tries a temporary-insanity plea for his client, played by Mare Winningham.