Yes, "slush puppie" is obviously a southern term, since I believe they originated in the U.K., and all the previous posters have mentioned having one in the southern states: i.e. Wisconsin, Idaho, New York :/
I think they are closer to a Mr. Mistee (or whatever the hell they call them) at D.Q. than a snow cone, slurpee or Icee
and just because you don't remember them doesn't mean they were never there
