I heard a story about someone who once worked at a KFC ... who decided ... to toss some ice cubes into the deep fryer ... then the whole fryer load of hot fat erupted and exploded into the ceiling...

I have thought about this for a while, and I think I know what happened.

The ice would be heavier than the hot oil, and it would sink to the bottom, where it would melt into water. The water, being even heavier than the ice, would all run to the lowest part of the fryer where it would remain, until it absorbed some 540 calories of heat per gram of water, at which point it would all flash over more or less instantaneously into steam (possibly even super-heated steam, given the increase in pressure caused by the weight of the oil above it). That steam would assume a volume many times greater than that of the water from whence it came, and a pressure many times greater than ambient and would displace the oil very quickly as it escaped to a lower pressure environment.

Does this sound right?

tanstaafl.