After kidnapping Princess Peach again, Bowser's plans are disrupted when he finds out that Bowser Junior is severely ill with Koopa Pox. With his youngest child on death's door, Peach finds herself seeing a side of Bowser she never thought existed.
Not a Monster contains examples of:
- Adult Fear: Bowser's youngest son is deathly ill and he can't do anything about it.
- Dead Guy Junior: Bowser named Morton Jr after his oldest brother.
- Even Evil Has Standards: Bowser kidnaps Peach and has tried to force her to marry him, but he doesn't try to make advances on Peach without her consent.
- Interspecies Romance: Between Bowser (koopa) and Peach (probably human). Peach finds herself slowly attracted to Bowser after seeing his more sensitive side.
- Jerk with a Heart of Gold: Bowser's a smug jerk who regularly kidnaps Peach, but he can also be gentle and affection when he wants to.
- Non-Mammalian Hair: Bowser can grow stubble.
- Related in the Adaptation: The Koopalings are Bowser's children, not his lackeys.
- Sick Episode: In the fic, Bowser Jr contracts Koopa Pox. Koopa Pox is much deadlier than Chicken Pox, with no adult having ever survived it and children only surviving if they're treated early.
- Sole Survivor: As children, Bowser's eight brothers died in a Koopa Pox outbreak. He was the only one that survived.
- Starcrossed Lovers: Bowser and Peach's romance is doomed to fail because of their different species.
- Theme Twin Naming: Bowser's twin brother was named "Bone".
- Twin Switch: As kids, Bowser and his twin brother would play pranks on their parents by pretending to be each other.
- Vague Age: It's hard to pin Bowser Jr's age, but he's treated like a 4-6 year old.