In 2007 a "documentary" called Zeitgeist became an internet sensation. It purported, among other things, that Jesus was simply a myth that plagiarized from more ancient mythological heroes. That is: Jesus never existed--some ancient people heard stories of other gods (Egyptian, Mesopotamian, Aztec) and simply created a hybrid of their own god, and thus Christianity was born.
That's simply gaga, lala nonsense.
This deliciously satirical, funny and witty video puts to rest any notion that Christianity borrowed from already existing myths.
So when we're at dinner over Christmas, and a teen announces, with a knowing swagger, that he/she doesn't believe in Christianity anymore because it's all a mish-mash of even older religious myths, we can respond with some facts.