Last one, and this one was just a bonus for Nyaasu, because she deserves it. :B Of course, it's a parody of Santa Claus is Coming to Town. Xehanort to me is one of the funniest villains ever, a genuine threat but also somewhat hilarious in how many times he pops up in some form or another. I mean, there's Master Xehanort, TerraXehanort, Ansem Seeker of Darkness, Xemnas… yeesh. Also, Xehanort in any form dressed as Santa Claus is hilarious. "Merry Christmas to all, and to all, Kingdom Hearts!"

I have no idea who owns the rights to Santa Claus is Coming to Town
When a Japanese company called Square-Enix and an American company named Disney fall in love, they give birth to a child they named "Kingdom Hearts." And Nomura saw that it was good. And that was the end of the eighth day.