Christmas Eve at the North Pole. Santa's alarm clock didn't go off, and he woke up 3 hours late for his epic run. In his rush to herd up the reindeer, they got spooked and took off into the forest. Santa had to go out on foot to round them up. 4 hours late... He loaded up the sleigh and Ho Ho Ho, off he goes.
Crack! He looks down and sees a broken sled runner, so he unloads the sleigh, jacks it up and goes out into the forest to cut down a tree and makes a new runner. 6 hours late now... He is not happy.
He has just finished re-loading the sleigh, when an angel appears, saying to Santa "Santa - where can I put this Christmas tree?" 'You can shove it up your a..e.' was the reply.
And to this day, that explains why the angel sits atop the Christmas tree.