Buffy the Vampire Slayer (8 p.m., WB) begins a flashback episode that crosses over into Angel (9 p.m., WB); Buffy learns all the sordid details about when Spike and Angel were pals, before an undead woman came between them. Juliet Landau returns as Drusilla. Who Wants to Be a Millionaire (8 p.m., ABC) continues its celebrity week, with Jon Stewart in the hot seat. Somehow, it's not as fun this time around, now that we know they're allowed to cheat. On Frasier (9 p.m., NBC), Frasier is not flattered when his boss begins imitating him. The new sitcom DAG (9:30 p.m., NBC) limps out of the gate. David Alan Grier (get it?) plays an inept Secret Service agent reassigned to the less important job of guarding first lady Delta Burke. Frontline (check local times, PBS) presents "Real Justice," a two-part documentary chronicling the day-to-day operations of a Boston county courthouse. On Once & Again (10 p.m., ABC), Eli wants to forget about the SATs and play in his garage band, but his parents have other ideas.
Magic at Kings (8 p.m., TBS)
Knicks at Sonics (10:30 p.m., TBS)
Sharks at Devils (7:30 p.m., ESPN2)
Blackhawks at Canucks (10:30 p.m., ESPN2)
Rosie O'Donnell (syndicated) Ben Affleck, Lily Tomlin
David Letterman (CBS) Bruce Willis, Charles Barkley, Arturo Sandoval
Jay Leno (NBC) Tobey Maguire, Steve Irwin, Natalie Cole
Politically Incorrect (ABC) Joy Behar, Tom Sizemore
Conan O'Brien (NBC) David Hasselhoff, Natasha Henstridge
Craig Kilborn (CBS) Nina Gordon
All times Eastern unless noted.