The further away in time we get from old shows, the more “never-before-seen” clips crop up. “The Carol Burnett Show: Let’s Bump up the Lights” (9 p.m., CBS) marks at least the third Burnett reunion in as many years. It promises plenty of scenes we’ve never seen before. This inspires several questions: Where have these clips been hiding? And if they’re so funny, how come we’ve never seen them before? Make no mistake, I liked the “Carol Burnett Show.” And, yes, the curtain-rod Scarlett O’Hara bit was comic genius. But I think I’ve seen it 400 times by now. Regulars Harvey Korman, Tim Conway, Vicki Lawrence and Lyle Waggoner return to recall the laughs, the cast’s esprit de corps and shared gags from the series that ran from 1967 to 1979.

• The National Geographic special “Dawn of the Maya” (7 p.m., PBS) offers new evidence of a highly advanced Mayan culture thriving hundreds of years before the Christian era. Long lost to history, recently excavated tombs and ruins point to an ancient city called El Mirador that boasted a massive pyramid and a population exceeding 100,000 residents.

Tonight’s other highlights

• Scheduled on “60 Minutes II” (6 p.m., CBS): diamonds, man-made in America, at a fraction of the cost of the real gems.
• Shuffleboard wars on “King of Queens” (8 p.m., CBS).
• George DiCenzo and Steve Railsback star in the 1976 made-for-television drama “Helter Skelter” (7 p.m., Lifetime Movie Network), adapted from prosecutor Vincent Bugliosi’s best-selling account of his case against cult-leader Charles Manson. A new version of “Helter Skelter” will air on Sunday on CBS.
• Fox offers a 10-minute trailer for the forthcoming disaster flick “The Day After Tomorrow” (7:44 p.m., Fox), followed by “American Idol” (7:54 p.m., Fox). With four contestants to go, you wonder how they can milk this for an hour and six minutes.
• Middle Eastern violence hits close to home on “The West Wing” (8 p.m., NBC).
• On back-to-back installments of “The Bachelor” (ABC): 23 rose-less lasses grill Jesse (8 p.m.), last week’s reject Trish insists on sacking her quarterback (9 p.m.).

Late night

Sen. John McCain and Tom Dreesen appear on “Late Show with David Letterman” (10:35 p.m., CBS) … Jay Leno hosts Jerry Seinfeld and Celine Dion on “The Tonight Show” (10:35 p.m., NBC).