TONIGHT'S MUST-SEE

"The Bachelor" finale, 9 p.m., ABC. At its peak, this show would stretch its finale over two hours of pounding music. Not any more. In a snappy 58 minutes, Brad has one final date each with DeAnna and Jenni, then makes a decision.

"Athens: The Dawn of Democracy," 9 p.m., PBS. For a hectic century, Athens experimented with democracy. Anyone, chosen by lot, could be a leader. Well, not anyone. Slaves — one-third of the population — couldn't. Nor could women, or anyone with a parent who wasn't born in Athens. Barely one in 10 qualified. With an economy boosted by the discovery of silver, Athens perpetually voted for war. It was a colonial power, then went too far by challenging Sparta. This fascinating tale is told by Bettany Hughes. In the tradition of the late Carl Sagan, she's an expert who happens to be exceptionally attractive, articulate and camera-savvy.

OF NOTE

"I Am an Animal: The Story of Ingrid Newkirk and PETA," 6 p.m., HBO. As viewers anticipate Thanksgiving dinner, HBO offers a disturbing look at animal rights in general and turkeys in particular. It also hears critics who insist PETA is better at fund-raising than accomplishments.

"Chuck," 7 p.m., NBC. Intent on his real romance with Lou (Rachel Bilson), Chuck ends his fake one with Sarah. Alas, Sarah may be jealous — and Lou may have a dark side.

"House," 7 p.m., Fox. The effects of the writers' strike start to be felt: Fox tosses in a distant rerun, with Chi McBride taking over as board chairman.

"How I Met Your Mother," 7 p.m., CBS. Marshall and Lily host their first Thanksgiving as a married couple.

"Ellen's Really Big Show," 7 and 8:30 p.m., TBS. Ellen DeGeneres says she loved the old variety shows. She hosts this one, adding comedy bits. Lyle Lovett performs and provides the show's band. Sheryl Crow and Mary J. Blige sing, sharing time with a magician, comedians and specialty acts.

"The Big Bang Theory," 7:30 p.m., CBS. In a change, CBS scrapped plans for a new episode tonight and replaced it with the pilot film. That has a few crude moments early but begins to click as soon as the two high-IQ guys meet their new neighbor, a bright-eyed waitress. In the episodes that followed, "Big Bang Theory" emerged as a happy surprise.

"Two and a Half Men," 8 p.m., CBS. Charlie can't help lusting for his future step-sister, played by Jenny McCarthy.

"Heroes," 8 p.m., NBC. This is expected to be a pivotal episode for Claire and her dad; he wants to move again, she doesn't. Also, Hiro returns from the distant past, learns of his dad's death, and heads to the more-recent past. And Suresh meets the intriguing Elle, then makes a key decision.

"Journeyman," 9 p.m., NBC. In the start of a two-parter, Dan tracks a possible serial killer in the 1990s.