My mom's birthday was right in the middle of our trip last October. I asked the front desk of the ASMo is there was anything special they do for birthdays. They said they would make a note of her birthday but couldn't guarentee they would be able to do anything.
The afternoon of her birthday when we returned to our rooms, she was greeted by a beautiful display of ballons in the front window along with a birthday card signed by the characters with a picture of Mickey and Minnie. They had also arranged all of my son's stuffed animals that were in there room around the window like it was a big birthday party of characters.
My mom was totally shocked as I didn't tell her that we told the front desk it was her birthday. She was amazed when I told her that WDW had done that free of charge. For years she had listened to me go on and on about the "magic" at WDW but I think she thought I was a bit crazy. When we returned to the parks we got her a badge that said it was her birthday and all the CMs kept coming up to her and wishing her a happy birthday. At our dinner at the Garden Grill that night the CM brought out a birthday cake (we never even requested it, she just did it when she saw the badge) and made a huge fuss about her birthday in front of everyone in the restaurant. All the characters came over and they led the restaurant in singing "Happy Birthday." My mom "gets" the "magic" now and says she can't imagine why anyone would go on vacation somewhere else!!