Back when Christmas started, coal was just as precious as firewood due it being a proper substitute for the latter, making it a gift by itself. Jump to present day, not only is coal no longer in mainstream use, it’s used as a joke gift for naughty children. This was perhaps Scrooge's biggest mistake when he proposed keeping Santa's version of Christmas a business venture. Coal wouldn't be a viable product to give or sell in the long term!
Of course Scrooge would come up with the idea of making Christmas a business venture. Take a good look at your local shops during the holiday season and tell me all those corporate retail executives didn't have the same idea.
Some savvy fans figured out that the reason behind Scrooge and Santa's falling out was over the monetization of Christmas all the way back in Season 1 when he was first mentioned in "The Impossible Summit of Mt. Neverrest!". Scrooge is the businessmen among businessmen and Santa is essentially the original charity worker. Given Scrooge's tendency to get involved in historical events, it is not that hard to put the two-and-two together.
Why Santa didn't try this plan years ago? He was waiting for Scrooge to learn to appreciate family and non-monetary rewards. Even now, with Scrooge finally being on good terms with his family again, and living with several kids, he still tried to sabotage Christmas in another attempt to turn it into a full business venture; doing this when he still was a full-time miser would have been a complete failure. Not to mention that, without the kids around, Scrooge would have kicked him out of the house the moment he arrived.
Just as likely, Scrooge met up with the Ghosts of Christmas Past/Present/Future not long after that and spent every Christmas Eve between then and the present day partying through time. Then in Season 1, the family spent Christmas climbing Mt. Neverest and in Season 2 was the last Scrooge and the Spirts spent the holiday raveling through time which Santa wouldn't have anticipated since it was so last minute. This year he had all 365 days to come up with the plan.
This episode would actually go a long way to explain why coal is the default "gift" for naughty children. Kids get to make a choice: they can be kind and loving like Santa and get the toys that Santa is offering, or they can be greedy and rude like Scrooge and get what he's peddling instead. However, as noted with the little girl at the end, this message can fall flat if the coal became a makeshift toy or is something they were actually looking for.
Back then, the coal could still be used to warm their homes, ensuring they wouldn't go cold in the winter. Even if he didn't give them a toy, Santa still proves he's a Nice Guy by giving them something to use rather than something to enjoy.
Plus, in a way, he's giving some credit to Scrooge's contributions by using his idea, even if not the way Scrooge wanted.
The episode suggests that Santa's workshop (formerly a home for elves) is at an Arctic woodland rather than the North Pole as commonly portrayed. This would be more practical, given the North Pole is nothing but frozen sea.
That would also square with the European tradition of placing Santa's workshop in Lapland, Finland.
The reason while the Ghosts of Past, Present and Future are absent, despite the last Christmas special making them regulars at the mansion during Christmas, is because they simply have already come and gone. The last special was set in the early evening, and this one starts with the boys being put to bed, setting it later in the evening, probably just after the yearly Christmas party.
Scrooge not knowing that coal is given to naughty children makes sense given that he's hated Santa since the very beginning of the operation. He's purposefully blocked all Santa-related things from his life ever since, so he's never had a chance to see what the symbolism of coal has become.
It also shows how genuinely behind the times he is. Not only does the average person not use coal anymore, but he hadn't realized in the many decades between first meeting Santa and present day that giving someone coal has become a symbol for naughtiness.
When Della tells her version of The Night Before Christmas, a scared Dewey asks for the original version, which Della doesn't give him. While this is probably just Della being overly fixated on the war tactics, it's also possible that Della legitimately doesn't know the original version of the poem due to Scrooge's hatred of Santa, either because she never learned it or because she's forgotten.
Launchpad's appearance at the end assisting Scrooge and Santa with giving gifts to children might seem like a friendly cameo after Put on a Bus after staying with Darkwing Duck and Gosalyn, but looking closely at the production numbers, this episode was one of two episodes (other than the Halloween themed episode The Trickening!) that were made before the rest of Season 3's episodes, therefore intending them to be placed anywhere in the season. With that in mind, Launchpad would've still been staying at Scrooge's mansion, therefore easily getting him to join the rest of the family to deliver gifts as opposed to getting him all the way from St. Canard.
Or, as said above, the Ducks could've picked him up when they flew over St. Canard (assuming this year he celebrated Christmas with Drake and Gosalyn).
Della says Santa knows what he did is not only a Call-Back to when the running gag first started but also highlights that she's just repeating Scrooge's words without knowing the whole story.
This two commenters under Seaniccus review of the episode sum up precisely Scrooge connection to coal in this episode:
dataweaver: What struck me about this was Scrooge's connection to coal. In some of the earlier versions of the Santa Claus story, he had a partner: Knecht Ruprecht, Krampus, Swarte Piet (“Black Pete”), and so on, with different parts of the world featuring different companions. These companions were darker than Santa Claus, punishing children on the naughty list with such “gifts” as a switch or a lump of coal while rewarding children on the nice list with simple but practical gifts. Scrooge isn't fitting into that mold perfectly (there's nothing in his character about punishing naughty children); but he comes surprisingly close.
B463L: I loved this element. There were so many layers here — the coal is a perfect symbol for Scrooge's industriousness and pragmatism. Like him, it's also misunderstood. People think of the coal as a punishment when, in truth, it's a useful, reliable commodity meant to keep you warm on a cold night. People think of Scrooge as a selfish, heartless miser when, in truth, he has an ethical objection to people receiving things they didn't earn, and he's principled enough to follow his convictions when it costs him dearly.
There's a reason why Bouncer is the only Beagle Boy that made it into the nice list: he has genuine concern about Bigtime obsession with kidnapping plots. This could be enough prove for Santa to include him on his nice list, despite Bouncers usual criminal acts which could've put him on naughty list.
Imagine if Webby and Santa didn't catch Scrooge. While Jennifer may have liked the coal (and seemed too young to understand what coal normally means on Christmas), imagine how everyone else would've have reacted. Not to mention, with the invoice from Scrooge, no doubt people would have been out for his blood.
It's likely Scrooge would have come clean to them, since meeting Jennifer is exactly what gave him his change of heart, and considering how forgiving Santa and Webby are, they'd forgive him and (probably) come up with the same plan to save Christmas for real this time.
, Finland.