The Polar Bears of Churchill with Ewan McGregor (PBS, check local listings): There they are, the huge land mammals living cheek-by-jowl with the citizens of a remote Canadian town on Hudson Bay. The bears fast for nearly six months in summer before returning to the frozen seas right through town. Fantastic photography is enhanced by amusing commentary from actor Ewan McGregor.
The Cosby Show: A Look Back (NBC, 9-11 p.m.): It was one of the best family comedies ever on television. It celebrated AfricanAmerican culture yet maintained its universal appeal. Members of the cast return to reminisce. Best of all, Cos himself introduces the subjects and demonstrates that he's still got it.
The Guardian (CBS, 9-10 p.m.): The season finale of this excellent drama series is a real cliffhanger. Simon Baker plays Nick Fallin, a corporate lawyer ordered to serve 1,500 hours of community service for a drug violation. Defending children and the poor, he has run into conflicts with his dear old dad (Dabney Coleman), whose business he hopes to inherit. The conflict escalates when Barton Fallin hands over the presidency to another colleague, while Nick tries to turn in a crack-head prostitute.
This week is season-and series-finale heaven. The networks trot out their best stuff for May sweeps. Look for "Saturday Night Live" (guest host Winona Ryder); "The Simpsons" (Homer's life is on the line again); "7th Heaven" (will Dad attend the wedding?); "Buffy the Vampire Slayer" (a two-part scorcher involving a sorceress); Rosie O'Donnell (bowing out of the talk-show circuit); "Felicity" (choosing at last between Ben and Noel); "NYPD Blue" (two hours of sorrow for Detective Sipowicz); and "The West Wing" (the ethics of dealing with terrorists plagues the president).