“Party Down” (9 p.m., Starz) returns for a second season and that’s cause for celebration. A strong ensemble cast with great chemistry play struggling actors, writers and assorted has-beens who work as cater-waiters on the periphery of Hollywood’s rich and famous.

Adam Scott stars as Henry, a once-promising actor whose talent was eclipsed by his role in a famous beer commercial. Lizzy Caplan (“Hot Tub Time Machine”) plays his former girlfriend, Casey, an actress forever on the verge and worrying that she’s about to be replaced by younger performers who look just like her. Martin Starr is Roman, the cynical writer of the group, a cerebral role not unlike his memorable turn as the terminally romantic cynic in “Adventureland.”

Megan Mullally joins the cast as Lydia, a nerdy and needy divorcee a tad older than the rest. Mullally seems to have as much fun with Lydia’s clueless repression as she did with Karen’s outsized personality on “Will & Grace.”

“Party” ventures to a new venue every week, with plenty of guest stars. Tonight, they cater a backstage party for Jackel Onassis, a Marilyn Manson-type who envies people with “normal” lives. In the coming episodes, they work at a preschool charity auction, where the competition can be vicious, and at a very sad and uneventful “orgy” for a recently divorced lawyer.

Over the course of the season, look for former regular Jane Lynch (“Glee”) to return in a guest spot. Other cameos include Kristen Bell, J.K. Simmons and Steve Guttenberg.

Following “Party Down,” Starz will launch “Gravity” (9:30 p.m.) an ensemble drama-comedy set in an outpatient clinic for suicide survivors. Not available for review.

• Series arrive, depart and resume, all over the dial. A crusading British chef bids adieu to Huntington, W.Va., on the season finale of “Jamie Oliver’s Food Revolution” (8 p.m., ABC).

Oliver traveled to Huntington, ranked as one of the unhealthiest cities in America, to change diets and attitudes. As expected, he’s hit some serious resistance in his attempt to get the city, and its school district, off its reliance on processed foods. In one last effort, he returns to a contentious city, with guest musical stars Rascal Flatts in tow.

• The weekly PBS news magazine “NOW” (8 p.m., PBS, check local listings) will air its last episode next Friday. Tonight, “NOW” glances back at its coverage of the ongoing wars in Iraq and Afghanistan.

• Cartoon Network launches the new ‘tween adventure cartoon “Generator Rex” (7:30 p.m., Cartoon Network). Set in the near future, after some kind Earth-shattering glitch, Rex lives in a world dominated by machine-human hybrids. Some of these creatures have mutated into monstrous calamities known as Exponentially Variegated Organisms (EVOs). Apparently, Rex is mutated just enough to shift shape at will. This gives him the power to both fight the EVO swarm and to “heal” the mutants. This last power should provide him with an endless supply of special friends.

Tonight’s other highlights

• Susan Sarandon explores her family tree on “Who Do You Think You Are?” (7 p.m., NBC)

• A sushi restaurant more cooked than rare on “Kitchen Nightmares” (8 p.m., Fox).

• A balcony collapse sends a couple to “Miami Medical” (9 p.m., CBS).