TV Insider

What's On: A Four-Way Superhero Crossover on The CW, Country Music on ABC, and Pentatonix on NBC

A critical checklist of notable Monday TV:

Supergirl-Arrow (8/7c, The CW): So Justice League got mixed reviews at the movies. DC's small-screen superhero franchises continue to chug along, and this week is the annual four-way crossover. The wedding of Barry Allen aka The Flash (Grant Gustin) and his beloved Iris (Candice Patton) is what brings the various do-gooders together, and the action begins when supervillain Nazis from parallel dimension Earth-X crash the party. The mayhem extends to Tuesday, where the story concludes on The Flash and DC's Legends of Tomorrow.

Holiday Music: Reba McEntire is the first-time host of ABC's eighth CMA Country Christmas special (8/7c), performing from her new My Kind of Christmas album. She's joined on Nashville's Grand Ole Opry stage by Kelsea Ballerini, Luke Bryan, Brett Eldredge, Alan Jackson, Lady Antebellum, Little Big Town, CeCe Winans, Trisha Yearwood Chris Young and more. … NBC brings back The Sing-Off a cappella champs Pentatonix for a second annual holiday special, A Very Pentatonix Christmas (10/9c), in which they're joined by the very busy Brett Eldredge, Voice coach Jennifer Hudson, America's Got Talent winner Darci Lynne Farmer and a special appearance by Jay Leno.

Holiday Movie: The first Christmas movie commissioned by Freeform since its rebranding, Angry Angel (9/8c) stars Jason Biggs as the angelic mentor of earth-bound celestial being Brenda Song, whose quest to earn her wings is complicated by romantic attachments to New Yorkers played by Ricky Mabe and Andy Favreau.

Diagnosis: Hit Show: The fall's breakout success story is ABC's The Good Doctor (10/9c), which this week presents Dr. Shaun Murphy (Freddie Highmore) and the staff of St. Bonaventure with the case of a boy from the Congo with severe congenital heart defects. But Dr. Shaun is also a bit rattled after another confusing encounter with his sexy neighbor.

Inside Monday TV: Never having recovered from the loss of Joan Rivers, E!'s Fashion Police (8/7c) returns for one final episode, hosted by Melissa Rivers, who looks back at the show's 20-year history with co-hosts Giuliana Rancic, Brad Goreski, NeNe Leakes and Margaret Cho. The special includes clips from a never-seen ’80s-themed episode featuring the immortal Joan. … In A&E's two-hour Dog and Beth: Fight of Their Lives (9/8c) docu-special, bounty hunter Duane "Dog" Chapman and wife Beth open up about Beth's battle with throat cancer, from diagnosis through surgery to recovery. … Filmed over two years by directors Brent and Craig Renaud, the HBO documentary Meth Storm (10/9c) examines the methamphetamine crisis and the war on drugs by focusing on an impoverished and ravaged community in rural Arkansas and local DEA efforts to stem the rising tide of abuse and death. … Having set such a low bar on the Jersey Shore, MTV now takes its cameras South to observe eight young adults acting out on the Floribama Shore (10/9c), set on the Gulf Coast's Florida Panhandle in Panama City Beach, where the beach is said to stretch all the way to Alabama. Alerting local authorities in both states …