A man with a white beard who lives in the sky decided to make a girl pregnant against her will, and some time in the Fall he was born a second time through her. Eventually people got all pissed off at him and strung him up on a cross until he died, but he wasn't really dead, and then he went back up to the sky again anyway.
And that's why we give presents in December.
And that's why we give presents in December.