Santa was very cross.  It was Christmas Eve and NOTHING was going
right. Mrs. Claus had burned all the cookies.  The elves were
complaining about not getting paid for the overtime they had while
making the toys.  The reindeer had been drinking all afternoon and were
dead drunk.  To make matters worse, they had taken the sleigh out for a
spin earlier in the day and had crashed it into a tree.

Santa was furious.  "I can't believe it!  I've got to deliver millions
of presents all over the world in just a few hours - all of my reindeer
are drunk, the elves are on strike and I don't even have a Christmas
tree! I sent that stupid little angel out HOURS ago to find a tree and
he isn't even back yet!  What am I going to do?"

Just then, the little angel opened the front door and stepped in from
the snowy night, dragging a Christmas tree.  He says, "Yo, fat man! 
Where do you want me to stick the tree this year?"

And thus the tradition of angels atop the Christmas trees came to 
pass.