“True Blood” (8 p.m. Sunday, HBO) enters its fourth season in full-fledged fantasy mode. It almost seems like the premium network wants the audience for the just-completed “Game of Thrones” to stick around.

As the action commences, Sookie (Anna Paquin) seems knee-deep in some kind of fairyland where time stands still and gorgeous folks devour a magical glowing fruit, an appetizer our heroine has the presence of mind to avoid. Not to give too much away, but action soon returns to her vampire Peyton Place by the bayou, where things are nuanced and interesting, if not a tad hard to follow.

Not unlike those glowing apples, “True Blood” is a decidedly acquired taste, even if its myriad subplots seem to have grown and multiplied like kudzu.

• NBC suits who long dreamed for Jerry Seinfeld to return to prime time probably never thought his vehicle would be reduced to summer filler. “The Marriage Ref” (9 p.m., NBC) returns for a new season on Sunday. For the uninitiated, this series asks three celebrities to referee husbands and wives in a domestic dispute of a quirky and humorous nature.

On tonight’s “Ref,” Seinfeld, actress Julianne Moore and “The Office” creator Ricky Gervais evaluate the competing claims of a man who thinks his Thai-born wife lets her mother’s visits last too long and a woman who thinks her husband’s habit of growing enormous pumpkins has become an obsessive distraction.

This year, the audience gets to vote on the show’s most emphatically right spouse, who wins a cash prize and will have a billboard erected in his or her hometown announcing the show’s verdict.

Hosted by Tom Papa, and sporadically amusing, “Ref” seems like a perfectly nice half-hour afternoon show expanded to a full 60 minutes in the interest of filling (or is that killing?) prime time.

• “Cocaine Sub Hunt” (8 p.m., National Geographic) recalls one of the most amazing drug busts ever — the discovery and seizure of a custom-made fiberglass submarine big enough for a six-man crew. More than 100 feet long, the vessel could carry 8 tons of narcotics with a street value estimated at a quarter of a billion dollars.

• A doctor theorizes a way to rescue “harnessed” kids on “Falling Skies” (9 p.m., TNT). Nearly 6 million viewers watched the debut of this alien invasion fantasy last week. That marks the largest series premiere on cable this year.

Tonight’s other highlights

• Scheduled on “60 Minutes” (6 p.m., CBS): homeless grammar school students; a profile of Wynton Marsalis.

• David Suchet stars on “Poirot XI: The Clocks” on “Masterpiece Mystery” (8 p.m., PBS, check local listings).

• A mountain hides evidence on “Leverage” (8 p.m., TNT).

• A murder appears to have been inspired by NASCAR on “The Glades” (9 p.m., A&E).