If you do a google search for Christmas (no quotes, just Christmas), you'll see the north pole along google's sponsored links. Seems to work for Google UK as well and Google DE. I think thats a pretty nice little search "easter egg". I wonder how many other ones are out there?
This doesn't tell me that they have manipulated any listings...just cleverly brought in a vertical line separator ( /images/cane2.gif ) next to the right side vertical Adwords displays when you type in Christmas (without quotes)...and the line separator is a big candy cane.... clever and really dresses up the page a bit for Christmas..