Santa and Shinny welcomed them all, and in exchange for the kindness and the sense of belonging they felt, each one of the elves, like Shinny had done before, gave a little portion of their own magic to Santa Claus. Because, if the big fella was to ever realize his dream, his great loving vision of bringing Christmas to the children of the world, he'd need all the magic he could get. The rest is, as they say, history.
As the centuries wore on and Shinny Upatree grew in stature among the other elves as their elder and leader. Santa Claus could always leave it to Shinny to make sure everything got done on time and in darned good order. Of course, Claus worried about his oldest friend, because in the last couple of hundred years, as the world population of children grew and grew and grew, Shinny's patience had grown shorter and shorter and shorter, because the work load had gotten heavier and heavier and heavier.
In an event still remembered centuries later, Santa and all the elves went to Shinny and told him that they'd all decided to take all the burden off him. They were going to be delegating out his work and actually dividing up Shinny's chores among everyone else. You should have heard him yelling, stomping and throwing furniture!!! As everyone ran for cover, they laughed, figuring Shinny's answer to their suggestion was..."NOOOOOOOOO!!!"
So Shinny is still in charge of all yearly preparations for the annual big night. And because he always manages to get the job done, everyone cuts him plenty of slack for his curmudgeonliness, because what it all comes down to is that without Shinny, the magic that is Christmas just wouldn't be the same.