This is a list of all enemies that are found in the coding of Mother 3, but cannot be encountered under normal gameplay circumstances. All enemy names derive from The Unofficial Mother 3 Fan Translation which, though unofficial, is the only English version of the game and was handled by an experienced team, among them Tomato, who has a background in professional localization.
Most unused enemies use Battle Sound 1 as their battle sound which falls under Code Numbers 439 for regular attack, 440 for Smaaaash! and 441 for Miss. All enemies, used or unused that have Battle Sound 1 have either More Mischievous Blues or Unfounded Revenge as their battle theme. These might somehow be related. Battle Sound 1 seems to be the default battle sound for enemies that were never actually given a battle sound (or in the case of a few enemies, no battle sound at all), much like More Mischievous Blues seems to be the default battle theme for unused enemies that were never given a battle theme. Further hacking (such as giving the enemies attacks using hacking software) is required for most of these to use their battle sounds as, by default, they have no attacks at all.