Santa was working furiously in the lead up to Christmas and this angel popped in and asked when he was going to put up his Christmas tree. Cant you see how busy i am trying to wrap all these presents yelled Santa, so bugger off.

A couple of hours later she stuck her head back in and asked the same question. Holy hell, Santa exploded and chased the angel out of his workshop.

A couple of hours later she stuck her head back in and said, i see you still dont have your tree up yet. With this, Santa grabbed
the little angel and said, i'm going to show you where to put your Christmas tree.

This is how that quaint tradition of putting a little angel on top of the Christmas tree started.