I covered this years ago, with Yahoo!'s Logo Surprise (Yahoo! Easter Egg). Basically, if you go to Yahoo.com and click on the exclamation point in the logo at the top, it will Yodel for you. The Yahoooooo yodel.
I am pretty sure Yahoo took this down for a while and probably recently added it when they launched the new logo placement a couple weeks ago. Here is a video of it in action:
In light of all the Yahoo news, this bit fun is always welcoming.
Forum discussion at DigitalPoint Forums.