Looking for absorbing programming? Nickelodeon celebrates its most popular property with a 24-hour “SpongeBob SquarePants” (7 p.m., Nickelodeon) marathon. The daylong saltwater sojourn culminates with the brand-new “SpongeBob” offering “The Best Day Ever,” airing at 8 p.m. Friday night.

As is customary, Patchy the Pirate (Tom Kenny) will host the proceedings. He can be seen driving around Manhattan in a giant party boat, introducing the cartoons and counting down the episodes. He will be joined on his urban yacht by hundreds of “SpongeBob” fans and various Nickelodeon stars and personalities. Will Linda Ellerbee join Patchy for Parcheesi? We’ll just have to wait and see.

For the uninitiated, or viewers older than 11, Spongebob is a sea sponge who wears what appear to be angular lederhosen. He may not be the brightest creature beneath the waves, but he projects an irrepressible optimism. Everyone is a potential friend, even anemones. But SpongeBob’s sunny personality is put to the test as he looks forward to “The Best Day Ever” with what has to be considered over-anticipation.

¢ Big changes are in store for the folks on “The Office” (7:30 p.m., NBC). Tonight, Michael’s long-suffering corporate supervisor, Jan, drops a major bombshell about the fate of the Scranton branch of the Dunder-Mifflin Paper Co.

The American version of “The Office” has come into its own over the past two seasons. But with this plot wrinkle, it appears to be following in the footsteps of the British series. In that version, the Slough branch was forced to merge with its rival, with layoffs made even more painful by Michael’s obtuse touch.

¢ It’s November sweeps, and nothing turns heads like stunt casting. Look for “Exorcist” star Linda Blair on “Supernatural” (8 p.m., CW). The star of “Born Innocent” and “Sarah T. – Portrait of a Teenage Alcoholic” will portray Detective Diana Ballard. Over the decades, Blair has guest starred in a number of series, including “Fantasy Island,” “Love Boat,” “Murder She Wrote,” “MacGyver” and “Married with Children.” She also hosted the cable series “Scariest Places on Earth.”

Tonight’s other highlights

¢ Jeff Probst hosts “Survivor: Cook Islands” (7 p.m., CBS).

¢ Catalina helps Earl complete his list on “My Name is Earl” (7 p.m., NBC).

¢ Betty takes advantage of a plum assignment reviewing posh hotels to get away from her family on “Ugly Betty” (7 p.m., ABC).

¢ On back-to-back episodes of “A Haunting” (Discovery), worries about an imaginary friend (7 p.m.), a haunted house in Utah (8 p.m.).

¢ A tiny crime-scene replica spells big trouble on “CSI” (8 p.m., CBS).

¢ A camping trip for the guys on “Grey’s Anatomy” (8 p.m., ABC).

¢ Sebastian prosecutes a child-killer on “Shark” (9 p.m., CBS).

¢ Abby and Kovac admit their need for a nanny on “ER” (9 p.m., NBC).

¢ Laura embarks on the dating scene on “Six Degrees” (9 p.m., ABC).