A scoop of ice cream, flavored syrup and milk, (a.k.a. the ice cream soda) dates back to 1876 in Philadelphia, thanks to a shop with an ice cream soda fountain, according to "The Oxford Companion to American Food and Drink." Wax nostalgic about soda fountains by watching "Back to the Future," "Pleasantville," or "Grease."
Or make your own with some vanilla ice cream and soda. But be aware, plopping a scoop or two of ice cream in a glass of soda won't create the same foaming effect as re-ordering the ingredients.
"When you pour soda over ice cream, the soda makes its bubbles as it usually does. But these bubbles don't just pop; they are held in place and stabilized by the thickening agents in the ice cream. You get a glass full of thick ice cream soda foam. If you add the ice cream after the soda, most of those soda bubbles have already formed and popped before the thickening agents can get to work," according to "A Moment of Science" on WIFU (Indiana Public Media).