The Google Docs team announced in a Google Groups thread that they have inserted a holiday easter egg in Google Spreadsheets. They said that if you are one of the first fifteen to find the easter egg and let them know what it is via this form, you will get Google Spreadsheets holiday schwag.
So go to Google Docs and sift through their functions to find the easter egg. Google did say that the easter egg was related to a function. The full function list might have it, but I doubt it, since it is an easter egg. If you find it, why not comment below so maybe Search Engine Roundtable readers can win also.
I tried to find it for about 3 minutes and I gave up. Decided to write this post to give you guys a shot at it.
Good luck!
Forum discussion at Google Groups.