Charles Dickens has written classics such as Oliver Twist, David Copperfield, A Tale of Two Cities and Great Expectations to name a few. While all of these works are iconic in their own right, none have been adapted quite as many times like his holiday classic A Christmas Carol. Even major franchises like Disney, DC Comics, Hanna-Barbera, Sonic the Hedgehog, and the Muppets have done their own takes on Dickens' holiday tale, using their own characters. It only made sense BBC's Doctor Who would have a go at it with the 2010 Christmas special.
The original novella by Dickens centers on a wealthy miser named Ebenezer Scrooge, who is obsessed with his money and treats the other people in his life terribly. He refuses to pay his employee Bob Cratchit a higher salary and turns down spending Christmas with his nephew Fred and his family. On Christmas Eve, Scrooge is visited by the ghost of his deceased friend and business partner Jacob Marley, who is paying in death for his sins in life. From there, Scrooge is visited by three ghosts: the Ghost of Christmas Past, the Ghost of Christmas Present and the Ghost of Christmas Yet to Come, all with the goal of getting Scrooge to mend his ways. When the latter gives him a glimpse of the miserable future that awaits him, that is enough to get him to change.
In the 2010 Doctor Who Christmas special "A Christmas Carol" by Steven Moffat, a sci-fi spin is given to the classic holiday story. In the opening scenes of the episode, the 11th Doctor's (Matt Smith) companions Amy Pond (Karen Gillan) and her husband Rory Williams (Arthur Darvill) are enjoying their honeymoon. They're on board a ship that's about to crash on a human-populated alien planet, thanks to being caught in the turbulent, electrical clouds owned and controlled by a wealthy miser named Kazran Sardick (Michael Gambon).
In an attempt to save his companions from doom, the Doctor appears to Kazran to plead with him to grant the ship safe passage into the planet, which the latter refuses. Having discovered his intense dislike for his father, Elliot Sardick, who invented the machine they use to control the clouds, the Doctor decides to travel to Kazran's past in order to change his present. From there, the Doctor ends up taking on the roles of the three Christmas ghosts from the original Dickens story.
A few decades into the past, the Doctor encounters Kazran as a small boy and summons a cloud shark into his room using his sonic screwdriver, though the shark ends up eating the screwdriver. This makes the shark sick, and to save its life, Kazran and the Doctor bring it to the cryogenic unit of the mansion where his father stores healthy, living individuals as "insurance" against people who are indebted to him. It's in the cryo unit that the Doctor and Kazran meet Abigail (Katherine Jenkins) who sings to the shark to calm it down. From there, they are able to get the shark back in the sky.
The young Kazran develops a strong liking towards Abigail, and the Doctor visits Kazran every Christmas in order to spend time with Abigail. Kazran as a young man ends up falling in love with Abigail, though he learns she has a terminal illness and letting her out every year shortens her lifespan. Upon learning this tragic detail, Kazran asks the Doctor to end their annual tradition and keeps Abigail frozen for many more decades in order to preserve her life. Though Kazran is grateful for the new happier memories, he once again becomes a bitter old man in the present, which doesn't help the Doctor save his companions from death.
In a last-ditch effort to save his companions and the lives of the passengers on board the crashing ship they're on, the Doctor fulfills his role as Ghost of Christmas Yet to Come by bringing the boy Kazran to the present (his future) to see the bitter, old man he has become. This horrifies both the young and old Kazran, who finally decides to help the Doctor save the crashing ship. Unfortunately, the changes the Doctor made to Kazran's past mean he no longer knows how to control the cloud machine and they are forced to revive Abigail one last time to have her sing into the broken sonic screwdriver to resonate with the shark that has the other half. This helps the ship land safely.
Of all the Doctor Who specials that have been made, "A Christmas Carol" is the first and only Doctor Who episode to genuinely feel like a holiday special and not like a story that just happens to take place on Christmas. It doesn't use any of the Doctor's classic monsters like the Daleks and Cybermen, but it does take place on a Christmas-themed alien planet where the residents all look like they were pulled out of the Victorian era. It's also the only holiday special that sees the Doctor attempt to change someone's life for the better as opposed to only showing up just in time to avert an alien invasion.