Arrow (CW, 8:00 p.m.) — The second night of a three-part CW network crossover is afoot. Tonight on Arrow, Gotham City meets Ruby Rose’s Kate Kane, the masked vigilante who shall soon be recognized as Batwoman. Kane will provide information to Supergirl and friends about why reality’s gone wonky.
The Great Christmas Light Fight (ABC, 8:00 p.m.) — The search continues to uncover the most outlandishly spectacular Christmas display in the U.S.
The Neighborhood (CBS, 8:00 p.m.) — Malcolm refuses to name the culprit who robbed him while Gemma learns an odd form of self-defense from Tina.
Happy Together (CBS, 8:30 p.m.) — A home-security system becomes a priority after a Cooper stalker gains entrance into Jake and Claire’s house.
DC’s Legends of Tomorrow (CW, 9:00 p.m.) — Constantine must face the consequences of tweaking the past, all while he and Zari attempt to hide this cardinal sin from the other Legends.
My Brilliant Friend (HBO, 9:00 p.m.) — HBO’s adaptation of Elena Ferrante’s novel gets real with a promise that might be broken.
Magnum P.I. (CBS, 9:00 p.m.) — Rick’s crush comes to Magnum for help after her illegal poker game gets interrupted by masked gunmen.
Bull (CBS, 10:00 p.m.) — A priest gets charged in a fatal hit-and-run, but he later refuses to divulge the name of the van’s actual driver to Bull and the TAC.
Nightflyers (Syfy, 10:00 p.m.) — Major changes are afoot for Rowan while D’Branin scores a breakthrough, and Lommie revisits the difficult past.
Pentatonix: A Not So Silent Night (ABC, 10:00 p.m.) — The holiday season gets a fresh infusion from the renowned a cappella vocal group, who invites celebrity guests to dole out classic tracks and modern jams.
LATE NIGHT GUESTS
Jimmy Kimmel Live!: Ellen DeGeneres; Pete Holmes, and Cole Swindell
The Tonight Show Starring Jimmy Fallon: John Mulaney, Vanessa Hudgens, and Grimes
The Late Show With Stephen Colbert: Bryan Cranston and historian Doris Kearns Goodwin
Late Night With Seth Meyers: Milo Ventimiglia, Jahana Hayes, and Lukas Graham
The Late Late Show With James Corden: Sean Hayes and Ice Cube