1) “The Simpsons,” 8 p.m., Fox. It’s the 30th annual “Treehouse of Horrors” and, in a nifty bonus, it’s “Simpsons” episode No. 666. That’s considered Satan’s number and this has lots of devilish fun. Homer trades a second son for an evil female spawn; he also keeps getting a new body for himself … and promptly ruining it. Milhouse hits a “Stranger Things” portal. And Selma (shown here has an affair with a fish creature. Parts of this are too harsh for some viewers; much of it is hilarious.
2) All night, National Geographic. Here is global exploration, big and ambitious: At 8 p.m. ET (rerunning at 11), Bob Ballard — who found the Titanic – seeks answers to Amelia Earhart’s 1937 disappearance. At 10 p.m.. (rerunning at 1 a.m.), Albert Lin begins a series searching for “lost cities.” That starts in Israel with the fortress of the Knighs Templar. Also, Titanic specials rerun from 5-8 p.m.
3) “Masterpiece: The Durrells in Corfu,” 8 p.m., HBO. Louisa should be happy now; her home (converted into an inn) is full of lodgers … and animals … and Spiro, the married man she loves. All is well, except that half her children have moved out; also, the townsfolk swirl with gossip. It’s a light, bright episode, but it closes with ominous crises, one personal and one globaL.
4) “God Friended Me,” 8 p.m., CBS. Well-meaning and sweet-spirited, this hour still falls flat. The focus is Joy (Jessica Lu), who’s been getting the “God account” messages lately; now she’s tugged by a personal crisis. That’s fine, except that the dialog is stiff and the plot is sort of senseless. Our heroes are torn by needing to be in two places; they never seem to realize they could split up and do both.
5) “Watchmen” debut, 9 p.m., HBO. This bizarre tale starts with some history: There really was a massacre in 1921 Tulsa, with blacks killed and their thriving business district destroyed. A fictionalized version propels us to an alternate world. Policemen wear masks so they won’t be attacked at home by vigilantes; one black cop doubles as a vigilante called Sister Night. She’s played by Regina King, one of many gifted actors (Lou Gossett, Jean Smart, Frances Fisher) in a well-made but perplexing start.