As his final project was being presented to the class, one of the students asserted that the chunks that made up the rings of Saturn were composed of ice. Prof. Caldwell asked, reasonably, "Water ice?"--as opposed to dry ice, or methane ice, or any other type of ice that exists in the solar system. The student immediately replied, "No, frozen."
It took a couple of seconds before anyone realized what the devil the student meant. He thought he was being asked whether the material was H2O in a liquid form ("water" ice, as in ice that had become water), completely overlooking the possibility that it might be an ice of some substance other than H2O. Prof. Caldwell started to correct the student, but gave it up as a lost cause, raising his eyes to the welkin for guidance, and shaking his head in exasperation. The titters among the students began slowly, increased to furtive laughter, and culminated in barely stifled hilarity, which continued for the rest of the class.
The phrase "No, frozen!" became a snide rejoinder among Forumites to any obtuse remark or stupid misperception.