Some info and a short description of this South Park episode on South Park Zone:
South Park - Woodland Critter Christmas is episode 125 and the last episode from the 8th season of the Comedy Central series South Park, and originally aired December 15, 2004.
In this South Park episode, Stan helps creatures that appear to be cute innocent woodland prepare for the birth of their Lord and Savior, the Anti-Christ and he must find a way to prevent this from happening. Santa plays an important role in this wicked adventure.
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(The complete plot for this South Park Episode)
This episode, which like many Christmas shows has an anapestic rhyming narration and storybook style, begins in the forest, where "the boy in a red poof-ball hat" which is Stan Marsh, discovers a group of sweet and innocent looking talking animals, the Woodland Christmas Critters, building a Christmas tree. Stan, who was very confused, was convinced by the animal to help them make a star for the tree before he goes home.Later that night, the animals from the forest come to Stan's room and wake him up explaining that one of the animals, a porcupine named Porcupiney, is pregnant with the creatures' Savior. Tired and drowsy, Stan agrees to help them build a manger for the baby. They then enlist his help against another problem: every year, they explain, one of the animals conceives their Savior, but every time, a ferocious mountain lion kills it before it gives birth to the baby. They insist that Stan is the only one capable of helping them. Stan, tired of this hole thing manages to kill the mountain lion, by tricking her into jumping off a ledge after him, but is dismayed to find that the lion was the mother of three cubs which are now orphans.
Stan is further horrified to discover that the woodland critters are, in fact, Satan worshipers, and that their Savior is actually the Antichrist, not The Son of God. They celebrate by sacrificing Rabbitty the Rabbit. Stan realizes that the mountain lion was only killing the woodland creatures to stop the Anti-Christ from being born.
After much persuasion from the narrator, Stan tries to stop the animals himself. But they easily rebuff him with their Satanic powers. Since it appears that only a mountain lion can kill the Antichrist, Stan returns to the mountains to enlist the orphaned cubs. The cubs, however, note that they need to learn "how to kill". earns what is happening, pulls out a SPAS-12 combat shotgun and slaughters all the creatures. He is about to kill the Anti-Christ, but Kyle — now free from the altar — declares that he wants the Anti-Christ to possess him, so that he can make the world better for the Jews. He allows the demon to possess him, and is about to unleash a devastating blow on the world when the story suddenly cuts away to Mr. Garrison's fourth-grade class, where it is revealed that everything that had happened so far in the episode was merely a Christmas-themed story Eric Cartman was reading to the class.
Kyle angrily objects, claiming that it is nothing more than Cartman's attempt to once again mock his believes at Christmas time. Mr. Garrison, fearing complaints from Kyle's mother, forces Cartman to stop. The other students, however, plead with Kyle to let Cartman continue because they want to hear the ending; Kyle objects that the ending is obvious, that Kyle, in the story, will be killed by Santa Claus so that Christmas is saved. Cartman says that is not the ending at all, and as the other boys persist, Kyle angrily and begrudgingly allows Cartman to continue.
Back in the story, Kyle suddenly declares that he can now feel that the Anti-Christ is pure cold, dark and evil and wants it out, while Stan responds, "What did you expect dude? It's the son of the Devil!" Santa, however, says that they have no choice but to kill Kyle, before the Anti-Christ can consume his soul and unleash his reign of terror.
Stan will bring the mountain lion cubs to help Kyle. Santa gives Stan a special Christmas wish, and Stan uses it to have Santa resurrect the mountain lion cubs' mother. Everyone then goes home to a happy Christmas.
And we see the old-fashioned classic title card reading "The End". The narrator then concludes the story by stating that "they all lived happily ever after... except for Kyle, who died of AIDS two weeks later". The Christmas song in the beginning plays over the ending credits.