Merry Christmas in Gotham

So you're checking your DVR for all those recorded reruns of this show; maybe there's a somewhat more humorous episode where the villains play poker, but you'd say this show's pretty dark, right? So what do they do when Christmas rolls around with all that holiday cheer? The Producers, heck, maybe even the people who typically write the show don't want you to air yet another dark episode with a Downer Ending, or even a Bittersweet Ending, it's Christmas! And thus this trope happens.

Merry Christmas in Gotham is when the tone of a Darker and Edgier series becomes Lighter and Softer, usually due to Executive Meddling resulting in a holiday episode. This can cause serious Mood Whiplash. The result is usually a strange Aesop-y episode in a series featuring at least some Gray morality of some sort. Whether or not this Mood Whiplash throws the episode into Narm territory is your call.

Note: This trope does not apply only to Christmas episodes, but holiday episodes of all sorts, but not any episodes that have nothing to do with holidays. That's just plain-jane Lighter and Softer taking effect.

Compare Mood Whiplash and Lighter and Softer. Contrast An Asskicking Christmas, Soapland Christmas, and Twisted Christmas.

Ending Trope: Spoilers Unmarked.

Anime and Manga

 * The Big O's Christmas special starts out grim as usual. We have a blind girl whose caretaker brother is a garbageman by day, and musician by night. They are starving, barely able to afford food at all. Then a mad scientist leaves a biological weapon in the boy's tip jar and it turns out the "weapon" is a massive self-growing Christmas tree made to teach people to love nature and each other. While the tree grows, everyone hears the boy's music and he is discovered. It's implied that they'll never need to worry about money ever again. D'awww.

Comic Books
"Daughter: This is my best Christmas ever! "Santa": Mine too, Ginny. Or at least -- the best in a long, long time."
 * The hilarious Superman/Batman Elseworld crossover Yes Tyrone, There Is a Santa Claus.
 * There's a Punisher story where Frank is about to snipe a druglord, when suddenly there's a little girl pulling on his coat telling him she's lost her dad. Frank stares at her and puts the gun away. When they find her dad, he starts to thank him before recognizing his chest emblem and starting to panic. Frank tells him to calm down, that he should really teach his daughter not to talk to strangers, and then leaves.
 * An issue of The Incredible Hulk dealt with Rhino and Hulk teaming up to be Mall Santa and Helper.
 * Batman Black & White, "A Slaying Song Tonight": A hitman plans to get near his target by taking the place of a Mall Santa hired to put in an appearance for the target's daughter. Batman figures it out in the nick of time and stops the hitman just before he reaches the house—then puts the costume on and does the Santa appearance himself.

Live Action TV

 * In the middle of the Doctor Who serial The Daleks' Master Plan, the Doctor and companions interrupt their saving the Second Great and Bountiful Human Empire from the Daleks for a Christmas Episode (the only missing Doctor Who episode confirmed by The BBC to have no spare copies hidden in private collectors' hands or a foreign TV station).
 * Eureka has an episode like this.
 * Warehouse 13 has Lighter and Softer Christmas episodes revolving around Christmas in some way.
 * Scrubs doubly subverts this one: The episode "My Own Personal Jesus" has Turk, initially so optimistic about Christmas that he comes into work with Rudolph antlers on, being ground down and losing his faith as seasonal alcohol-related injuries and attempted suicides clog up the hospital. Just when it seems like Turk is ready to give up surgery, though, a star leads him to a missing girl who ran away from the hospital, and he helps her give birth beneath a Christmas tree, and the episode ends on a prolonged Golden Moment played straighter than usual and with an unusually strong relgious message for the show.

Western Animation

 * Batman the Animated Series has the episode "A Bullet for Bullock", where Batman is asked for help by, of all people, Harvey Bullock, and the Aesop is that you should always be helping people, even if they don't like you.
 * Danny Phantom features an all-round Christmas Spectacular as Danny who is trying to spoil the event. Unusually for a children's show, Danny loathes Christmas, but with good reason.
 * In an episode of ReBoot, Big Bad and otherwise Complete Monster Megabyte goes to great lengths to infiltrate Enzo's birthday party, with no more heinous goal than to play electric guitar, put on a rocking show (including a duet with Bob), and leave.
 * Kim Possible: Ron tries to take on Drakken by himself so Kim can have a nice Christmas with her family. Ends up with Ron and Drakken bonding over an old TV show, whose theme they sing together. Now, Kim Possible isn't exactly dark and edgy to begin with, but they were shooting for more Lighter and Softer than usual.
 * Subverted with the Christmas episode of Batman the Brave And The Bold. The series is usually pretty whacky, but it takes on a darker edge with . May also be a Seventh-Episode Twist.

Real Life

 * During World War I, a Christmas truce broke out. A Christmas tree was erected in the middle of the battlefield and the allied and axis forces gathered together to sing Christmas carols. There was music, dancing, hot drinks, and a few friendly games of soccer shared. For one day there were no soldiers, just young men celebrating Christmas.
 * In the days of czarist Russia, on Easter Eve, at midnight, a child killer escaped from prison. The sentry on duty raised his rifle to shoot the criminal, but then the church bell rang in Easter, the sentry's eyes welled with tears of Easter joy, he hadn't the heart to kill the fugitive and he threw his rifle to the ground. etc.