Last year was the first year that Mobile 'raised' their Moon Pie but it was such a success they're doing it again this year.
Over in Tallapoosa, Georgia, they do a possum drop each year (it's a... well he's... um... it's a taxidermied possum). Afterwards you can visit and have your picture taken with him.
Other Southern towns are dropping local icons like a pickle, pelican, gumbo pot, beach ball, peach, chicken, and a hog - there's a list of what cities all over the US drop/raise here. I'd go for the gumbo pot.