* AbusiveParents: The Sewer King sees himself as a good parent to his "beloved children", even though he orders them to steal for him, punishes them severely for talking, and makes them live in deplorable conditions.
* AdultFear: Batman is logically angry when Frog picks up and plays with a decorative gun on the wall of Wayne Manor, since it could have been loaded.
* EvilCannotComprehendGood: The Sewer King couldn't understand why Batman would bother saving his life.
* TheFagin: The Sewer King is the evil version
* FirstTimeInTheSun: In the end, the Sewer King's captured orphans are brought into the sunlight at last.
* KingOfTheHomeless: The Sewer King.
* LightIsNotGood: The Sewer King punishes a child for breaking his rule against "talking" (he cried out after injuring himself) by locking him in a room filled with bright lights for several hours.
** Averted at the end when the orphans enter the daylight again.
* MonsterOfTheWeek: The Sewer King.
* PapaWolf: Batman was ''enraged'' by Sewer King's crimes against the orphans.
* RecklessGunUsage: While being chased by Alfred in the Wayne mansion, Frog finds a collection of antique firearms. He grabs a blunderbuss off the wall and waves it around like a toy. Alfred immediately backs off, but Batman jumps in and grabs the gun out of the boy's hands. Batman notes, "It's not loaded, but it could have been."
* SaveTheVillain: Given the nature of the villain's crime, Batman seriously thought about averting the trope this time but it was eventually played straight.
* SuddenlyVoiced: Frog gets a line at the end of the episode.
* TheVoiceless: The Sewer King, believing that children should be seen and not heard, forces his charges to be silent at all times...or else.
* ThouShaltNotKill: Batman still goes by this, but he let the Sewer King know that we was very tempted to break it this time.