Wizard 101 had a fairly extensive update early this morning, so don't be surprised if the game takes quite awhile to load the next time you play. (I'm posting this while mine's working on it.) And what did they do?
Decorate for the birthday party, of course!

From their announcement page:
Come join the party!We've decorated the Commons, Shopping District and Ravenwood with streamers and balloons to make the world more festive!
And what's a party without a party hat! Each player will receive a party hat!
To receive your hat, follow these steps:
1. Go to
Wizard101.com the website
2. Log in to the website with your Wizard101 login and password.
3. Click the words "Redeem Card or Code" under your name.
4. Click "Wizard101 Promotional Codes"
5. Enter the code "party" and click Continue - follow the instructions on those pages to receive your hat!
The next time you log in to Wizard101, your hat will be waiting for you.
Thanks for celebrating with us and see you at the party!

It's one party hat per account, but it's tradeable so you can put it in your shared bank and let all your characters take turns wearing it. Unfortunately it's not dyeable, pink's not really my color. I saw another girl with a pink hat as well, so I'm guessing the boys get blue. If anyone has both boy and girl characters, let me know if the hat changes color depending on who's wearing it.