The long-running “Doctor Who” franchise prepares for the departure of the current physician, David Tennant, with three episodes shot in HD. “Doctor Who: Inside the TARDIS” (7 p.m., today, BBC America) glances back at Tennant’s tenure on the program. “Doctor Who: Waters of Mars” (8 p.m.) finds the doctor on the Red Planet’s Bowie Base in the year 2059, where the H2O proves less than potable.

Fans who just can’t get enough Tennant can find him on a special “Who”-themed installment of “The Graham Norton Show” (9:30 p.m.), featuring an interview with Tennant as well as clips from his past appearances.

• Even the most dedicated fans of “CSI”-style morgue dramas may choose to turn away from “Raw Anatomy: Inside the Elephant” (7 p.m., today, National Geographic), a documentary look at the autopsy of a 12-ton Asian elephant whose cause of death remains a mystery. It takes a hydraulic crane to perch this pachyderm on the slab.

• The film history series “A Night At the Movies” (7 p.m., Sunday, TCM) celebrates the blockbuster with “The Gigantic World of Epics,” a survey of really big movies from the silent era to the present.

Movies really moved beyond Nickelodeon novelty distractions with the 1915 release of director D.W. Griffith’s “Birth of a Nation,” a three-hour historical drama presented on a vast scale. And the epic’s boom-and-bust pattern was established a year later when Griffith’s ambitious “Intolerance” all but capsized his career.

People have long associated Hollywood with its ambitious epics, larger-than-life adaptations of literary classics, biblical accounts and popular novels, from the silent 1927 “King of Kings” (11 p.m.) to “Doctor Zhivago” (11:30 a.m.) and “Ben Hur” (3 p.m.).

Look for interviews with actors, directors and executives from Kenneth Branagh (“Henry V”), John Milius (“The Wind and the Lion”) and Steven Spielberg (“Saving Private Ryan”).

Epics have long been the way Hollywood differentiated itself from television’s small screen. The rise of the medium coincided with the blockbusters of the 1950s, most notably “The Ten Commandments,” a film that still gets great ratings when aired during the Easter/Passover season.

While epics went out of fashion during the 1970s and 1980s they have returned with big movies like “Gladiator” and the “Lord of the Rings” trilogy. TV audiences continue to respond to the genre. While the ratings for the Academy Awards have declined over the years, they always seem to perk up when big, big movies like “Titanic” or “Lord of the Rings” receive their Oscars.

• Talk show host George Lopez presides over this year’s annual “Christmas in Washington” (7 p.m., Sunday, TNT) concert. An eclectic array of talent includes singers Mary J. Blige, Neil Diamond, Sugarland, Rob Thomas and Usher.

The concert will also feature a performance by 15-year-old soul singer Justin Bieber, a self-taught musician proficient in drums, guitar, piano and trumpet who gained popularity from his homemade online video interpretations of artists including Ne-Yo, Usher and Stevie Wonder.

His self-broadcasting venture attracted more than 50 million viewers, landing him a record deal and a chance to meet the President and First Lady tonight and perform for a national TV audience.

• “Two Weeks in Hell” (7 p.m., Sunday, Discovery) follows would-be Army Special Forces Green Berets as they endure a grueling basic-training process that separates the wheat from the chaff.

Today’s highlights

• Rob Lowe and Kimberly Williams star in the 2002 holiday tear-jerker “The Christmas Shoes” (6 p.m., Lifetime).

• Will Ferrell brings a manic innocence to his title role in the 2003 holiday comedy “Elf” (7 p.m., CBS).

• Missives to the big man get rerouted in the 2008 special “Muppets Christmas: Letters to Santa” (7 p.m., NBC).

• Tim Allen stars in the 2002 sequel “The Santa Clause 2” (7 p.m., ABC).

• Chevy Chase stars in “National Lampoon’s Christmas Vacation” (7 p.m., AMC).

• Professional wrestlers step into Bob Hope’s shoes, entertaining soldiers on “WWE Salute to the Troops” (8 p.m., NBC)

Sunday’s highlights

l A winner emerges on “Survivor: Samoa” (7 p.m., CBS). The cast then returns for the “Survivor Samoa Reunion” (9 p.m.).

l Tim Allen dons a fat suit and a red suit for the third time in the 2006 sequel “The Santa Clause 3” (7 p.m., ABC).

l “Masterpiece Classic” (8 p.m., PBS, check local listings) repeats the 2007 adaptation of “Cranford,” starring Judi Dench and Eileen Atkins.

Cult choice

A twister spins a farm girl (Judy Garland) from gray Kansas farm to a technicolor illusion in the 1939 fantasy “The Wizard of Oz” (6 p.m. and 8:15 p.m., today, TNT). And her little dog, too.