Tasty's post about doing a xmas tree reminded me of something...
It was Xmas eve , and things in the North Pole were not going to plan. Santa Claus woke up with a bad stomach, probably caused by the prawn vindaloo he'd eaten the night before. Mrs Claus had a migraine. When he went to the stables to check on the reindeer, they were half-drunk, thanks to some lingonberry liqueur some idiot had left lying around. 
The elves were laughing all over the place, because someone had made some cannabis brownies and left them in the kitchen. 
Santa bellowed at the elves, and finally, they got the show on the road - about 2 hours late. 
Got into his sled, with the tipsy reindeer, and headed off to Norway, Sweden and Denmark. On landing in Denmark, he realised  that the gear box on the sled was playing up, and he could only manage half speed. By the time he landed in London, UK, he realised he needed a good, stiff drink, so he strode into the St Nicholas Arms and ordered a double scotch. 
3 minutes later, a bouncy fairy came up to him with a tree under her arm. 
"HELLLOOOO, SANTA CLAUS! How are you? Wonderful to see you ! First time ever! Can I get a selfie? Are you on my Instagram? Can  I give you a hug??? Oh, by the the way, someone gave me this tree and told me you'd know where to stick it! Lovely! " (boing, boing, boing)
Santa slid off his bar stool and thundered: 
"YOU CAN STICK YOUR BLOODY TREE UP YOUR.....!!!!"
And that, folks, is why there's always a fairy on top of a Christmas tree.