When a specific genre has an unwritten or implied rule, and one or more characters simply ignore it and break it without hesitation.
The Rule: In games, movies, or series involving killer mascot horror, the night guard or person who encounters them will, at most, flee, run, hide, and maybe use some furniture to conveniently kill, damage, or ward off the animatronic or killer doll.
The Rule-Breaker: Nicolas Cage / The Janitor ignored all of these rules. Not only did he not fear the animatronics in the movie, but he personally turned them into walking metal punching bags. They expected a defenseless victim, but instead got a janitor who is not only completely fearless, but every bit as terrifying as they are.
As one character put it: "He's not trapped in here with them, THEY'RE trapped in here with HIM.
The Rule: Serial killer characters should never use firearms. They aren't aesthetically flashy, they ruin the typical slasher's "art" of grotesque violence, and they usually can't be used to inflict slow, painful deaths.
The Rule-Breaker: Art generally avoids guns, but if things get serious, spiral out of control, or he simply gets too annoyed, he couldn't care less about whether a firearm "ruins his aesthetic charm." He will straight up pull out a gun and blast whoever is in front of him right in the face, LOL.
The Rule: In shonen or battle anime, there is an unwritten rule that when a character is about to transform, everyone else just stands around doing absolutely nothing. They politely wait out the flashing lights and dramatic metamorphosis, and only then does the fight resume.
The Rule-Breaker: Eren completely ruined the Warhammer Titan's flashy transformation sequence by smashing its face in right in the middle of it. Honestly, he saved the MAPPA animators a ton of work XD
I bet a lot of animators wish more characters would do them a favor and break this rule more often XD
The Rule: Usually in horror, inanimate objects or entities only move when you look away, blink, or lose line of sight, much like SCP-173 or the Weeping Angels.
The Rule-Breaker: The Rolling Giant initially plays along with this rule, completely tricking the protagonist into thinking they are safe as long as they keep their eyes on it. But just when he thinks he has it figured out, the giant straight-up starts rolling toward him in plain sight, shattering the illusion and attacking without waiting for him to look away.
The Rule: In stories that follow the classic Hero's Journey, there is an unspoken "requirement" that the mentor must die. This death serves to give the protagonist a reality check, spark their ultimate evolution, and raise the stakes of the entire story.
The Rule-Breaker: The anime constantly hints at and plays with the idea that All Might is destined to die. However, not only is that future rewritten, but All Might actually survives to see his apprentice become Japan's greatest hero and graduate high school. Even though he can no longer fight by Deku's side, the mere fact that he lives to witness his successor's success completely shatters this traditional Hero's Journey trope.