I was flying AA from DFW to MCI on my 23rd birthday and mentioned to the Gate agent jokingly that I should get an upgrade because it was my birthday. She laughed and said she would if she could but I wasnt even elite at that point and she just wished me a happy birthday and took the next passenger.

So I board and take my coach seat and right after the forward doors are closed, the first class FA comes to my seat and only says "let me see your drivers license". Then she see's that it really is my birthday and says come with me and leads me to a first class bulk head seat. It was great! She was extra nice to me the entire flight! Apparently she had been standing near the gate when i talked to the agent and had overheard that it was my BD.