PRETTY LITTLE LIARS: Aria (Lucy Hale) helps the girls look for proof to clear Spencer’s name. (Eric McCandless/ABC Family)

(All times eastern)

On a special Christmas-themed installment of “Pretty Little Liars” (ABC Family at 8 p.m.), the girls come together to help clear Spencer’s name before the holidays and a mysterious, ghostly presence shows itself to Alison.

The four remaining junior chefs — Abby, Adaiah, Logan and Samuel — are challenged to cut as many perfect filets as possible from an Alaska king salmon for a restaurant-quality dish on “MasterChef Junior” (Fox at 8).

Barry comes face-to-face with his ultimate nemesis, Reverse Flash, and plans with Cisco and Wells to trap him on “The Flash” (CW at 8).

The definitive 1970 animated film “Santa Claus Is Comin’ to Town” (ABC at 8) explains the legend of Santa Claus and how he began delivering presents to children worldwide on Christmas Eve. Fred Astaire, Mickey Rooney and Joan Gardner lend their voices to the classic tale.

“Rickover: The Birth of Nuclear Power” (MPT at 8) profiles Hyman G. Rickover, the Navy admiral who harnessed atomic power to drive the first nuclear-powered submarine, the USS Nautilus.

More classic holiday ephemera is found on “Rudolph the Red-Nosed Reindeer” (CBS at 8), the 1964 animated musical that tells the story of the reindeer with the incandescent nose.

The members of the gang on “New Girl” (Fox at 9) prepare for their holiday trips, but they end up stranded in the many terminals of LAX.

Annie, Kay and Dennah make Gil realize that he depends far too much on Jake, but the discovery shakes the group up in the wrong way on “Marry Me” (NBC at 9).

With the holidays swiftly approaching, Mindy starts to wonder whether Danny’s planning to propose on “The Mindy Project” (Fox at 9:30).

“NBC News Special: Angelina Jolie: Unbroken” (NBC at 10) has the movie star and director sitting down with Tom Brokaw to talk about her latest film, “Unbroken,” which is about Louis Zamperini, the Olympic track star an World War II hero.

Taylor Swift, Ariana Grande, Ed Sheeran and Hozier perform, and supermodels, such as Adriana Lima and Karlie Kloss, take the runway in London to showcase over-the-top lingerie on “The Victoria’s Secret Fashion Show” (CBS at 10).

Comedian Ricky Gervais and musician-turned-actor Steven Van Zandt are on “The Tonight Show Starring Jimmy Fallon” (NBC at 11:35), with music from ILoveMakonnen.

Actors Ben Stiller and Olivia Munn come to the “Late Show With David Letterman” (CBS at 11:35), with musical guest LaLa Brooks.

ESPN’s Chris Fowler and Kirk Herbstreit stop by “Jimmy Kimmel Live” (ABC at 11:35), with music from Priory.

Rachel Lubitz