In the 60's, the Thriftways in the Deep South sold an ice-cream novelty that you dropped into a glass of soda water and it became an ice cream soda. I can still remember the exciting volcanic fizzing, not to mention the taste, which was really chocolatey (to a six-year-old). It may have been crossed with a float, but it was definitely mixed with soda water. Canada Dry soda water to be exact....clear bottles...
Anybody else heard of these so I can prove I'm not hallucinating?