Thursday's Highlights: 'Thurgood' on HBO
Naked Science: A new installment surveys various theories about the origins of the Grand Canyon (4 and 11 p.m. National Geographic).
Community: Greendale holds student-body elections in this new episode of the sitcom (8 p.m. NBC).
American Idol: The top 20 semifinalists are revealed on tonight's results show (8 p.m. Fox).
Rules of Engagement: Jeff (Patrick Warburton) tries – and fails – to get some alone time in this new episode (8:31 p.m. CBS).
CSI: Crime Scene Investigation: The team probes reports of zombies on a new episode of the crime drama (9 p.m. CBS).
The Office: Traveling salesman Todd Packer (guest star David Koechner) angles for a desk job on a new episode of the workplace satire (9 p.m. NBC).
Nikita: Amanda (Melinda Clarke) sedates and interrogates Alex (Lyndsy Fonseca) in this new episode (9 p.m. KTLA).
Grey's Anatomy: Peter MacNicol (“Ally McBeal”) guest stars on a new episode of the hospital drama (9 p.m. KABC).
Laugh Out Loud Comedy Festival: Collin Moulton is featured in the stand-up series' season finale (11 p.m. Showtime).
Ben-Hur: Charlton Heston stars in this epic 1959 historical drama (7 p.m. TCM).
Basketball: The Heat battle the Bulls (5 p.m. TNT) and the Celtics face the Nuggets (7:30 p.m. TNT).
Hockey: The Kings welcome the Wild (7:30 p.m. FSN).
College basketball: The UCLA Bruins host Arizona State (8 p.m. FS Prime).
Photo: Carol Rosegg / HBO