Blending two metaphoricalexpressions that have the same meaning, mainly to see if people are paying attention or to create an amusing visual. Randomly blending any two expressions that do not have the same meaning, or tacking on to the metaphorical expression with a rogue ending is a botched attempt at blendaphoring.
Botched blendaphor examples: As American as killing two birds with one apple pie. You can lead a horse to water but you can't make him drink prune juice.