No matter what you're celebrating, Disney probably has a button for it, or you can write in your own celebration. Pick one up at any indoor merchandise location or at Guest Services.
Between Future World and World Showcase, you'll find a kiosk that will get you started on your own adventure around World Showcase. There are several to choose from. You'll get a phone in order to play and find and save Agent P from Phineas and Ferb.
Fun for all ages.
If you're at Disney Springs, hit up the Ghirardelli Chocolate Factory and get a free sample of their wares.
Got your "It's my birthday!" button on? You are more than likely going to get a free dessert at Disney restaurants. Woohoo!