There's nothing that Timmy Turner loves more than granting wishes (and Tootie)! It's just too bad that all of a sudden, Timmy accidentally knocks Santa Claus into the present maker, giving him amnesia, and now Santa thinks he's the Easter Bunny, and Christmas is just around the corner! Now it's up to Timmy to save Christmas, but not before a dangerous and snowy magical journey to visit Elmer the Elder Elf to get his name off the Naughty List first! Can Timmy survive the journey and save Christmas before it's too late?
The film begins a few days before Christmas at the North Pole, where Santa Claus is looking over his Nice and Naughty Lists, the latter of which he receives from the Keeper of the Naughty List, Elmer the Elder Elf while the elves were silent when Elmer's around. Just then, he sees children's names and their wishes starting to disappear from his Nice List, because those children's wishes are already being fulfilled. Santa demands to know who is causing this.
At that moment, it is revealed that the cause of Santa's problem is coming from the now-grown-up Timmy Turner, who is traveling the world with his girlfriend, Tootie, and his fairies, Cosmo, Wanda and Poof, granting wishes for all unfortunate people in the world as part of the Wishful Thinking business that they started at the end of Grow Up, Timmy Turner! As the group stops off back in Timmy and Tootie's old hometown of Dimmsdale, they catch the attention of Timmy's deranged former schoolteacher, Denzel Crocker, still determined to capture Timmy's fairies. However, while following Timmy, Crocker runs into some of his students and shows them some of his typical hostility, saying that he doesn't like Christmas because his mother always gave him handbags ("she always knew I'd give them back to her"), and he always got coal from Santa. The kids mention that Crocker is obviously on the Naughty List and, when he asks them where he can find it, tell him it's kept at the North Pole, but he refuses to believe the place (or polar bears) really exists.
Timmy and Tootie briefly cross paths with Timmy's parents, who are working downtown as a Salvation Army Santa and his assistant and thinks that Timmy is going back to them. After Timmy makes it clear to them that he is not moving back in with them, Timmy's mom tells the young couple that she has asked Santa for a new computer, and Timmy's dad says he wants a magical pony who poops ice cream, eats the ice cream,poops gold,eats the gold,and poops out a motorcycle then Timmy's mom and dad will all ride away in their motorcycle. Right after Timmy's parents leave, though, a pair of elves named Dingle Dave and Christmas Carol show up, demanding to speak with Timmy. When Cosmo and Wanda see them, they start trading insults with the two elves before they tell Timmy that Santa Claus wants to see him personally, for he is in big trouble. Using their own flying minivan, Dave and Carol bring Timmy, Tootie, and the Cosmas to Santa's workshop at the North Pole, where they are greeted by Jingle Jill, who acts just as hostile towards the fairies. Tootie becomes curious to know why the fairies and elves are feuding as Jill brings them inside the workshop. As Jill is giving the group a tour of the workshop, Santa shows up and greets Timmy and Tootie.
Unbeknownst to them, Crocker stowed away on the bottom of the elves' minivan and is astonished to see that the North Pole exists (as well as polar bears, one of which briefly chases after him). He then sneaks into the workshop though an open window and tries to disguise himself by snatching one of the elves' hats. However, one of the real elves catches Crocker and, figuring that he is a new employee here, assigns him to cleaning out the reindeer stalls (but not before putting his ears through an ear-sharpener). After he finishes cleaning out the reindeer pen ("Who knew reindeer poop was so sparkly?"), though, Crocker makes the mistake of leaving the gates open, allowing the reindeers to run loose.
Santa explains to Timmy that because he has been using Cosmo and Wanda's magic to grant the Christmas wishes of all the children in the world, it's causing them to give up on Santa. He tells the pink-hatted adult that "with great power, and that includes magical fairies, comes great responsibility," and after Timmy apologizes, Santa gives him two candy canes, saying there isn't any bad spot a candy cane can't get him out of. Just then, one elf tells Santa the gift-making machine has gotten jammed again, and when Santa goes to look at it, saying "I wish this thing would stop breaking down", Timmy decides to have Cosmo and Wanda grant that request. However, as a result of trying to use fairy magic inside an elf-made building, the magic instead turns into a blast that causes Santa to fall into the gift-making machine. When he emerges from the machine, it is shown that he has gotten amnesia and starts thinking he is certain other beings like the Easter Bunny. To make matters worse, the whole workshop then starts shutting down because Santa is out of commission.
Jorgen Von Strangle suddenly arrives and points out to Timmy that he now has to assume Santa's responsibilities, for it is written in Da Rules that a godchild must take over the role of a holiday icon if the godchild has harmed them to the extent that they cannot do their job. Carol brings Santa's hat to Timmy, and when he puts it on, it seems to work, as the workshop starts repowering, but only for a short while before it crashes again. Tinsel Ted explains that Timmy actually cannot be Santa because he has gotten himself on the Naughty List. Timmy figures maybe he can just have Cosmo and Wanda zap his name off of the Naughty List, but it turns out they are unable do anything about it because, with the Christmas spirit being depowered, the North Pole's magnetic polarity is now nullifying the fairy magic. Dave and Carol explain that the only way Timmy can get his name off the Naughty List is to find Elmer the Elder Elf, the only one who has the power to do so, but they tell him that this will be a very difficult and likely deadly task. Despite the warning, Timmy is willing to accept the challenge, and Tootie volunteers to come with him, along with the fairies (though Cosmo really doesn't want to go). Crocker then reveals himself and tells Timmy that he is also coming along, since he also wants his own name removed from the Naughty List as well.
Timmy and the others begin their journey, bringing along Dave and Carol as guides, though it becomes apparent that the two elves do not actually know the way to Elmer's realm, and they keep bickering with Cosmo and Wanda. The group comes to the Cracked Candy Cane Chasm (a chasm full of razor-sharp candy canes spikes) and manage to get over it using the zip-line above it. However, as soon as they make it past the chasm, the ground cracks underneath them, and Timmy and Crocker are separated from the others. Timmy's fairies, the elves, and Tootie come across a penguin who has somehow ended up at the North Pole, and Tootie starts communicating with it in the penguin language, asking if it can help them find Timmy and Crocker. The penguin doesn't know where Timmy is, but it is able to help them find their way out of the forest they've gotten lost in.
In the meantime, Timmy and Crocker find themselves near a cliff, and Timmy is trying to save Crocker, and he reveals that he doesn't really need glasses and he just wears them to look smart. Crocker falls and then they both realize that it wasn't a cliff after on. Later, the two come upon a quartet of large sentient gingerbread men - Ginger-Ted, Ginger-Ed, Ginger-Ned, and Ginger-Jed. The four gingerbread men are very friendly to Timmy at first, but then the starving Crocker starts eating Ginger-Jed, which angers the other three enough to want to kill the two humans. While running from the angry gingerbread men, Timmy and Crocker reunite with the others just as they've made it out of the forest. Dave and Carol manage to fend off the gingerbread men by throwing snowballs at them, forcing them to retreat.
That night, the group sets up camp and Timmy tries to start a fire, but has trouble keeping it going because the leaves are too wet to burn. Crocker, showing some kindness for once, lends the coal he has always received from Santa and allows Timmy to use it in the fire. After Timmy gets the fire going, Cosmo and Dave briefly start bonding over eating marshmallows, and Tootie congratulates her boyfriend on granting her wish to make a fire even without magic. Back at Santa's workshop, the elves and Jorgen notice that the Christmas spirit is getting weak, and as a result, Christmas gloom is starting to take over. The gloom is shown taking its effects on the citizens of Dimmsdale, including Timmy's parents, making them all too depressed to enjoy Christmas (though it has the opposite effect on Vicky, Tootie's evil sister).
The next day, Timmy and company reach the Bridge of Badness, a heavily damaged bridge over a boiling river of eggnog that is the last obstacle standing between them and Elmer's lair. Timmy starts crossing the bridge and almost loses his footing, but Poof manages to give him a boost. The rest of the group is then forced to follow Timmy across the bridge immediately when they see the vengeful gingerbread men coming after them again. Cosmo, Wanda, and Poof manage to take down Ginger-Ed and Ginger-Ned with snowballs, but Ginger-Ted starts sawing the rope holding up one end of the bridge. Crocker just barely makes it across right as the bridge falls entirely, and he reveals that he dyes his hair black and he is a redhead. But in attempting to pull his old nemesis up to the other side, Timmy falls off the cliff. The others, especially Tootie and the fairies and even Crocker, are all saddened that Timmy appears to have died, but it turns out that he actually survived, having climbed back up the cliff using the two candy canes Santa gave him earlier.
The group finally makes it into Elmer's house and come face-to-face with the Elder Elf himself. Timmy asks Elmer why he is on the naughty list when he has been granting wishes for others. Elmer explains that it's technically Cosmo, Wanda, and Poof who've been granting the wishes, but while Timmy no longer makes wishes for himself, he still doesn't think of the consequences of the wishes he has been having the fairies grant for other people. The Elder Elf then proves his point by playing video clips showing things that have happened as a result of several reckless wishes Timmy used his fairies to grant at the beginning of the film, including his attempt to help Santa that has now resulted in endangering Christmas, and for that, he refuses to take Timmy's name off the Naughty list. Timmy apologizes to the others for his failure to save Christmas, though Tootie is still proud of him for doing his best. But Crocker reveals that, after years of battling him, he has finally come to respect Timmy for having the courage to risk his life to save theirs. Elmer, having overheard that speech, is impressed that Timmy's kindness was able to change Crocker's shriveled heart and officially takes Timmy's name off the Naughty List. He then allows the group to use his own vehicle to get back to Santa's workshop. As he went back inside his home, he saw his Eiffel Tower made of toothpicks destroyed and demanded who did that.
After they make it back, Timmy quickly puts on Santa's suit, bringing the workshop back to full power. However, the elves explain that Timmy has a very small chance of saving Christmas now that gloom is starting to block the path out of the North Pole. Since they only have an hour left to get things ready, Timmy tells everyone that they need to work together, and even Jorgen, having had to deal with the amnesiac Santa while they were gone, is more than willing to help them. They manage to get the sleigh filled on time, but the reindeer are still gone due to Crocker accidentally letting them loose earlier. Fortunately, Cosmo, Wanda and Poof manage to bring in the Wishful Thinking van to use as a substitute. With Jorgen and the Cosmas driving the van, Timmy, Tootie, and Crocker take off in Santa's sleigh, just barely making it through the gloom in the sky. With that, Timmy and the others manage to successfully deliver all of Santa's presents to everyone (including the computer and pony that Timmy's mom and dad wanted).
On Christmas morning, Santa, now having recovered from his amnesia, is surprised to see that all his work has been taken care of for him, and he joins everyone for the Christmas party they're now throwing. Dave and Carol present Crocker with a new tie, which he is happy to receive because it is the first real present anyone has ever given him despite not being cleared from the Naughty List. Dave and Carol also finally make amends with Cosmo, Wanda, and Poof, thanking them for helping save Christmas. They also reveal to Tootie that the reason the fairies and the elves were feuding in the first place was because the fairies never returned a power drill they borrowed from the elves two thousand years ago; in actuality, though, the fairies did return the drill, leaving it on the elves' back porch. Timmy and Tootie then say "Merry Christmas" to each other and share a kiss under the mistletoe.
This movie attracted 4.473 million watchers on its premiere night, and posted impressive triple-digit gains over last year. The premiere also bested its closest competitor (Disney) by triple-digits, with K2-11 (7.2/2.4 million, +140%), K6-11 (8.3/1.7 million, +152%) and T9-14 (5.7/1.2 million, +119%) and total viewers (4.5 million, +164%).
It became the 5th most watched program on Nickelodeon of 2012.
"A Fairly Odd Christmas" gained mixed reviewes from critics. Common Sense Media gave the film a 3 stars out of 5. Robert Lloyd from Los Angeles Times said the movie does "a nice job" honoring "their animated originals", but criticized the lack of originality in the script. In general, the movie was largely criticized for having a too complex story line and "confusing details". However, it was much praised for the well-done blending of live-action and CGI.