In a nod to “Mickey’s Christmas Carol,” Scrooge avoids the pressures of the holidays by traveling back in time with a trio of fun-loving ghosts to crash history’s greatest Christmas parties instead. Meanwhile, time-lost Dewey teams up with young Donald Duck to find his mom on Christmas.
It's Christmas Eve in McDuck Manor, and Donald, Huey, Louie, Webby, and Duckworth, are all getting into the spirit of the season. However, true to his name, Scrooge hates every second of "crass commercialism, empty sentiment, and all the trappings of the holiday". After destroying an animatronic Santa Claus and, to Webby's delight, declaring "Bah, humbug!", he heads to his room.
In the triplets' bedroom, Dewey is alone, wistfully staring at an old picture of his mother and wishing her a merry Christmas. Donald walks in and invites the boy to join in the family celebration, but Dewey maintains that he wants to be by himself. Once Dewey is alone again, he spots a mysterious green light and follows it to Scrooge's study, to find his great-uncle surrounded by three strange spirits. Scrooge initially pretends to fight the ghosts, but eventually admits to Dewey that the spirits are old acquaintances of his -- the Ghost of Christmas Past, Ghost of Christmas Present, and Ghost of Christmas Future. Scrooge and the Ghosts have an annual tradition of time-traveling to history's greatest Christmas parties every Christmas Eve, the one time Scrooge takes a break from all his other responsibilities, and his apparent hatred of Christmas is all an act to keep this to himself (except for his passionate dislike of Santa Claus; he does not explain why this is).
The Ghosts and Scrooge fly through time to the First Annual McDuck Enterprises Christmas Party. Scrooge is initially delighted, but he is quickly mistaken for his younger self by the other party-goers and is dragged into various business responsibilities, missing his chance to be part of the festivities and being robbed by Grandpappy Beagle and the Beagle Boy trio of Bankjob, Babyface and Bugle Beagle. Scrooge explains his frustration to Christmas Past, who sends Scrooge and himself to Scrooge's first Christmas in Duckburg. While it's certainly quieter than the last trip, Scrooge quickly grows bored with no company but the spirit. At that, Scrooge has an epiphany: "The minor frustrations of your life pale in comparison to the excitement they bring: hearth, home, family. That's what Christmas is all about!" He thanks the spirit for this lesson and asks to return to the present, but to Scrooge's surprise, this angers Christmas Past. Every year, Past and his fellow spirits teach a different person "the true meaning of Christmas", only for the spirits to be forgotten from then on. Scrooge McDuck is the only one who welcomes them year after year, and expresses contempt that Scrooge now plans on leaving them too in exchange for his family. The Ghost plans to trap Scrooge with him in the past, but Scrooge tricks him into leaving his magical time-traveling umbrella. Scrooge takes the time-brella for himself and leaves the Spirit behind.
Concurrently with the flight of Scrooge and the Spirits, Dewey surreptitiously sneaks along in Christmas Future's cloak. He drops himself off twenty years in the past at another Christmas Eve in McDuck Manor. Dewey is thrilled to have the chance to spend Christmas with his mother, but when he enters, all he finds is a preteen Donald during his emo phase. Claiming to be "Bluey", a very distant cousin of the Ducks, he asks where Della is. When young Donald explains that Della is outside doing their usual tradition of hunting for Santa Claus, "Bluey" strong-arms him into helping him look for her. Dewey then heads for Della's tent, with young Donald not far behind. Seconds after arriving however, they find the tent deserted, and seeing the tree stained with jelly, not Della's blood. As the two know Della can't set the family-sized tent up alone, they spot duck footprints as well as those of a larger animal.
The two continue to trek through the woods with Donald wanting to be a loner not caring much about adventuring with Della. It was to seem Donald had rejected going a Christmas adventure with his sister, and they spot her scarf hanging from a tree. But then, a massive creature called a Wendigo appears yelling at the two. Donald tries to outrun the monster by hiding in a tree and falls off giving him away. After some running, Donald and Dewey are ensnared in a net and someone matching Della's description appears, but she is younger. Della is disappointed her prey was not Santa Claus, and Donald throws a temper tantrum, but Dewey almost recognizes her. Della tells the two she wants to capture Santa and present him as a trophy to Scrooge. Della also says the Wendigo is a poor soul who turns into a monster by obsession and desperation, while Donald calls out "Dumbella" which annoys his sister. Della insists Donald apologize and tries to make up some excuses as he hasn't seen her all night long. Dewey realizes Donald's younger incarnation wanted to keep himself in his room instead of spending Christmas with Della.
Donald apologizes for abandoning Della on Christmas and she cuts them loose. She then asks the Wendigo what it wants and it calls out to Scrooge. The younger Ducks then fight the monster and it knocks Della back to her net, giving her and Dewey and idea. Donald continues until the Wendigo knocks Donald off and breaks his guitar. Fuming with rage, Donald beats the Wendigo ferociously and knocks it into Della and Dewey's net. The three then drag it back to McDuck Manor's front door. After Donald again apologizes, Della thanks Dewey who hugs her. Dewey excuses that Della is his cousin from his great-grandmother's niece's side, but young Della sees through the fabrication as it was the fourth weirdest thing that happened on Christmas. Dewey was also about to warn young Della and Donald about the events of the future, but both of them refused to listen, believing it would disrupt the time stream.
Young Della then tells Dewey to stay where he is, while she and Donald were going back into the mansion to let their uncle Scrooge deal with the beast. But during which time, the Wendigo unties itself from the rope and is about to attack Dewey, but present Scrooge arrives and knocks the beast to the ground from the sky. Scrooge is surprised to see Dewey in the past, as he was flying Future, Present and himself back to the present when he spotted him in front of McDuck Manor. Even with Scrooge's backlash, an emotional Dewey hugs Scrooge and asks him to take them back to their family. Meanwhile, the Wendigo's head begins to crack until it is revealed that Past has been the Wendigo the entire time. Feeling remorseful and realizing that Past has been in the woods waiting for Scrooge to return after so many years, Scrooge gives Past back his time umbrella, claiming that no one gets left behind on Christmas. The group then fly back to the present, where Past, Present and Future introduce themselves to the other present residents of McDuck Manor.
In a flashback, Donald and Della are seen gifting their presents to one another. Della gifted Donald an oversized Christmas sweater, something which Donald still wears every Christmas to this day, and Donald gifted Della a new scarf, something Della has worn all the time up until the present. When Dewey returns to the Manor, he and Donald share a warm hug as Donald says to him "welcome back", leading Dewey to wonder whether or not Donald remembers the events of the past Christmas. Later on, the family then sing a different version of the twelve days of Christmas song with Launchpad playing the piano. Meanwhile on the moon, Della is seen looking at a photo of her, Donald, Scrooge and her triplets before they had hatched which she had kept with her ever since her crash on the moon. She wishes her family a merry Christmas from afar, and hopes to be seeing them again soon. She is last seen working on something from a station she made for herself from the parts of the Spear Of Selene.
There are several references made to "Mickey's Christmas Carol" throughout the episodes. The illustrations that are shown during the episode's closing credits are created by animator Michael Peraza, who served as a layout artist on "Mickey's Christmas Carol" and was asked by the DuckTales producers to create DuckTales illustrations in the same vein.
The episode's title appears to reference the Wham song Last Christmas.
Mrs. Beakley refers to a Christmas movie entitled "Christmas on Bear Mountain"; this is a reference to the very first comic book story in which Scrooge McDuck appeared.
Scrooge references Jormungandr, the World Serpent or Midgard Serpent of Norse mythology.
Young Donald refers to young Della as Dumbella.
Young Donald has a poster of an egg underwater in his room, this might be a reference the Nirvana album "Nevermind".
Scrooge meets a man at the Christmas Party in the past named Rhutt Betlah who is going on about square rocks found in the Andes. His name is a reference to the character Rhett Butler from Gone With The Wind. The story about the square rocks is a reference to a 1949 Donald Duck comic story written by Carl Barks entitled "Lost In the Andes". In that story Rhutt Betlah is said to have discovered a valley in the Andes in the 19th century where square chickens laid square eggs.
Young Donald also exclaims “quackarooni!” during the fight with the wendigo. This was a catchphrase of the boys in the original series.
Bankjob, Babyface and Bugle all appeared occasionally in the original Ducktales in place of the usual trio (Bigtime, Burger and Bouncer) but were phased out after the first season in favor of the other three (and Baggy). Their appearance in the past (while also never appearing in the present) may be a reference to this.
When the Wendigo was attacking Dewey and younger Donald and Della, he presumably shouted "wendigo," but in actuality he was shouting When'd he go? as reference to Past wondering when Scrooge went off to.