Due to wiki policy, ALL SPOILERS ARE UNMARKED. You Have Been Warned.
- When Heart asks how Mad Rat is going to kill the scientist, Mad Rat says that he is going to bash in the scientist's head. Mind you, despite being a half-zombie with rhythm and time powers, he is still a rat. Instead of biting the scientist then have him die of the many diseases rats have, he actually thinks that his tiny rat body has the strength that can bash in a human head.
- Mad Rat's animation cycle has him swap between various "cool" poses when he dashes to the beat... except for one where he's faceplanting.
- After Mad Rat defeats a zombie rat mob, he faints. The Rat God nonchalantly explains that he is asphyxiating... something that happens to rats a lot.
- Heart apparently does not find anything wrong with drinking sewer water.
- Heart tries to reason with Mad Rat by telling him that he could leave his mark on the living world in other ways. Mad Rat then demonstrates... by leaving an actual mark of his face on a sewer pipe. Heart laughs off how poor the drawing is... which was on purpose, since Mad Rat wanted to demonstrate why not every way of leaving a mark would be effective. This becomes a Brick Joke when he sees the ghosts of the rats he eliminated but, after Heart slaps some sense into him, he finds that he was acting scared of his old doodle.Mad Rat: This must be a joke.
- Really, every time Heart slaps Mad Rat out of his delusions counts. Once Heart slaps Mad Rat before a cat could eat Mad Rat, Mad Rat asks for a gentler way out of his delusions. Heart retorts that the cat would have eaten Mad Rat before Heart found a gentler way. Prior to 4-2, Mad Rat finds himself inexplicably back at the laboratory without realizing he had just been in the forest outside of the city, upon which Heart slaps Mad Rat and the background suddenly changes back to the forest.
- After Mad Rat reaffirms his desire of getting rid of the Rat God:Rat God: Don't you remember? I live in your head!
Mad Rat: Oh, yeah?! Where's rent?!
Rat God: I already paid it! The chance for a re-do!
