TONIGHT'S MUST-SEE

"Chuck," 7 p.m., NBC. Poor Chuck has two things to worry about. One is his effort to be an assistant manager at Buy More. He faces a tough competitor. The other: He's being pushed into his first secret-agent mission. This requires him to be smooth and savvy; it also requires him to dance the tango. The result is a fun hour, with action, humor and a spy tale. Bright and buoyant, "Chuck" is one of the best new series.

"Heroes," 8 p.m., NBC. With a huge cast left over from the first season, there are plenty of characters still waiting to return. Tonight, Niki and Mikah are back; she hopes to leave Las Vegas and start a new life. Also, Suresh is back in New York; he finds a painting by Isaac that foretells a death. Meanwhile, Hiro's hero finally does some good, in ancient Japan. And Maya uses her deadly abilities to help her brother.

OF NOTE

"The Naked Brothers Band," 5 p.m., Nickelodeon. If you missed this special over the weekend, catch it now. Nat feels challenged by a strutting rocker who even woos Rosalina. It's a silly story, instantly redeemed by the easy charm of Nat and Alex Wolff, ages 12 and 9, the show's stars.

"Prison Break," 7 p.m., Fox. Michael plans a daring escape. Meanwhile, Linc gets an ominous warning.

"How I Met Your Mother," 7 p.m., CBS. Ted doesn't have much time to feel sorry for himself. Two women simultaneous fall for him.

"Celebrity Expose" (7 p.m.) and "Control Room" (8 p.m.), MyNetwork (KFVE). This struggling network aims young. Its first hour profiles Britney Spears; the second hour is a concert by John Mayer.

"Big Bang Theory," 7:30 p.m., CBS. Leonard is distraught that Penny, the beauty who moved in next door, is dating. This propels him to actually date someone himself.

"Two and a Half Men," 8 p.m., CBS. Charlie keeps being criticized for dating young bimbos. Now he tries someone his age, played by Ming-Na.

"Journeyman," 9 p.m., NBC. Just as Dan and his wife start to warm up to each other again, there are two setbacks: He time travels, and she learns he's been seeing his former girlfriend in other time periods.