*** UPDATE 9/6/12 ***
It appears that they have revamped their rewards program and you now have to pay for a membership. There is no mention of any FREE Birthday offer any longer. Several other movie theaters do offer FREE Birthday Stuff (see below).
Become a member of the AMC MovieWatcher Rewards club. Once you have an active account you’ll get an email coupon for a FREE fountain drink for your birthday.
►►► Hollywood Theaters – FREE Birthday Popcorn ◄◄◄
►►► Harkins Theatres – FREE Birthday Popcorn ◄◄◄
►►► Redbox – FREE DVD Movie Rental ◄◄◄
►►► More FREE Birthday Stuff ◄◄◄