That’s a whole different ball of fish

This is a mix of two phrases with the same meaning – “different ball of wax” and “different kettle of fish” (completely different or not at all similar).   Fish ball soup might also be in the unconscious here (see picture).   This type of malaphor involving phrases with the same or similar meanings is also referred to as a congruent conflation and is usually the most commonly uttered malaphor (and usually the best).  Loyal follower David Spain unintentionally blurted this one out and referred it here.  Thanks David!