A lavish, sometimes shaky but overall glorious second season of “Downton Abbey” ends on “Masterpiece Classic” (PBS, 9 p.m., check local listings) with a remarkable two hour “Christmas episode” that first aired in the U.K. during the holidays (odd, they bask in special episodes at a time when the U.S. mostly has reruns). Storylines are wrapped, directions for next season are suggested and the one big lingering mystery (which has really never been a mystery to close watchers) is resolved.

The new comedy from Ricky Gervais and Stephen Merchant, “Life’s Too Short” (HBO, 10:30 p.m.) is likely their funniest since the original version of “The Office.” In this case, the guy who’s delusional and full of himself is the small person actor Warwick Davis. And he’s just the right guy to test an almost scientific approach to humor – poking fun at things surrounding touchy subjects but not the subject itself. A Liam Neeson bit in tonight’s opener is uproarious in that regard.

It accompanies a vibrant episode of “Eastbound & Down” (HBO, 10 p.m.) which finds Kenny Powers back in the U.S., playing for a Myrtle Beach minor league team and the show itself on its best footing yet. A longer review of it I wrote for Salon can be found here.

It’s always a pleasure to welcome a new season of “The Amazing Race” (CBS, 8 p.m.). Among the 11 teams is a pair of professional clowns and a recycled reality couple—Brendon and Rachel of “Big Brother.”

Less welcome is the new season of “Celebrity Apprentice” (NBC, 9 p.m.) full of rehashed reality stars and former stars smelling of desperation. Among them: Dee Snider, Clay Aiken, Cheryl Tiegs, Arsenio Hall, Lou Ferrigno and George Takei. The first challenge has the two teams, men and women, opening sandwich shops and hoping to raise the most money for charity. Trump’s boardroom is excruciating; and some people wanted this guy to run for president?

“The Simpsons” (Fox, 8 p.m.) reaches an amazing touchstone: its 500th episode. WikiLeaks founder Julian Assange guest stars as himself as the family finds itself exiled from Springfield.

One thing Comedy Central can do surprisingly well are thoughtful tributes to comics who die. The latest one comes tonight in “I Ain’t Scared of You: A Tribute to Bernie Mac” (Comedy Central, 10 p.m.) .

A number of guest stars return to “The Good Wife” (CBS, 9 p.m.) including Parker Posey, Rita Wilson and Amy Sedaris.

Mo’ non-zombies, mo’ problems on “The Walking Dead” (AMC, 9 p.m.).

“Comic Book Men” (AMC, 10 p.m.) is certainly the most entertaining “Pawn Shop” style show around.

Joan Allen is a pretty good love interest for Dustin Hoffman’s character on “Luck” (HBO, 9 p.m.).

If Jasmine is throwing an end of the summer bash, it’s pretty assured you’ll want to be there on “Shameless” (Showtime, 9 p.m.).

Fresh back from Whitney’s funeral, the star and director puts the dress back on for “Tyler Perry’s Madea goes to Jail” (TBS, 8 p.m.).

“Khloe & Lamar” (E!, 10 p.m.) start up a new season, as does that other reality show couple “Ice Loves Coco” (E!, 10:30 p.m.).

France is still the setting for the Oscar films on Turner Classic Movies with “The Song of Bernadette” (8 p.m.), “The Razor’s Edge” (11 p.m.), “Roberta” (1:30 a.m.) and “The Last Metro” (3:30 a.m.).

NBA action includes Mavericks at Knicks (ABC, 1 p.m.), Magic at Heat (ABC, 3:30 p.m.) and Nuggets at Thunder (ESPN, 8 p.m.).

Sunday Talk

ABC: Sen. John McCain, Robert Gibbs. CBS: Rick Santorum. NBC: Reps. Paul Ryan and Chris Van Hollen. CNN: Reps. Ron Paul and Michele Bachmann, Gov. Mitch Daniels. Fox News: Newt Gingrich, Rep. Eric Cantor.