“Warrior Challenge” (8 p.m., PBS, check local listings), takes men culled from the ranks of servicemen and fire and police officers, and transports them back to the distant past to learn how Romans, Vikings, knights and gladiators lived, ate, slept and fought. If you think wielding swords and javelins is tough, just try wearing underwear from the second century! Like “Manor House,” this four-part re-enactment series is both addictive and educational.

• It didn’t take long for Kimberly Caldwell of “American Idol” (7 p.m., Fox) to find a new gig. The Texas native has been hired as a special correspondent on the Fox Sports Network show “54321.”

Tonight’s other highlights

• Jess’ estranged dad (Rob Estes) arrives on “Gilmore Girls” (7 p.m., WB).
• Nick and Burton differ over corporate strategy on “The Guardian” (8 p.m., CBS).
• Martin has doubts about his son’s paternity on “Frasier” (8 p.m., NBC).
• Jack finds the hacker behind the crucial recordings on “24” (8 p.m., Fox).
• Avril Lavigne, Korn, Limp Bizkit and Sum 41 perform numbers by their favorite band on “Icon: Metallica” (8 p.m., MTV).
• Caroline Kennedy appears on “The Daily Show with Jon Stewart” (10 p.m., Comedy Central).

Series notes

Mac takes a CIA assignment on “JAG” (7 p.m., CBS) … “Most Outrageous Game Show Moments 4” (7 p.m., NBC) … An unexpected invitation on “8 Simple Rules” (7 p.m., ABC) … Buffy vs. Caleb on “Buffy the Vampire Slayer” (7 p.m., UPN).

Incriminating evidence on “Platinum” (8 p.m., UPN) … Lana asks Clark to explain a ghostly visitor on “Smallville” (8 p.m., WB)

Ellie pads her resume on “Watching Ellie” (8:30 p.m., NBC) … Claude’s little brother (Richard Ruccolo) flirts with Lydia on “Less than Perfect” (8:30 p.m., ABC) … Amy mulls a teen’s proposed marriage on “Judging Amy” (9 p.m., CBS) … Scheduled on “Dateline” (9 p.m., NBC): a glance at the hospital drama “ER.”

Late night

Hugh Jackman and Kelly Clarkson appear on “Late Show with David Letterman” (10:35 p.m., CBS) … Jay Leno hosts Dennis Miller, Famke Janssen and Fabulous on “The Tonight Show” (10:35 p.m., NBC).

Mekhi Phifer chats on “Late Night with Conan O’Brien” (11:35 p.m., NBC) … Lacey Chabert appears on “The Late, Late Show with Craig Kilborn” (11:37 p.m., CBS).