Once the birthday person (be it a child or an adult) has on their button, you will here Happy Birthday's throughout the parks from the CMs. They must be "trained" to keep an eye out for them. I had one for my birthday, and did not have it pinned on my shirt, but on the strap of my purse,and I had Happy Birthday's coming at me from all directions. DD9 had a "Happy Birthday" Tiara on in the park on her birthday, as we ate at 1900 Park Fare, and that drew lots of attention from CMs and the characters.