That sounds like Dippin' Dots (http://www.dippindots.com/home.asp), 'The Ice Cream of the Future'. It's ice cream that's dropped shot-tower style into LN2, and frozen into tiny, brightly coloured spheres. The vendor has tubs of different flavours, and you can mix and match right on the spot. They've had them at the Indiana State Fair since the early 90s, but in looking over their website, they seem to be a midwestern company, so they might be a novelty elsewhere.