Reggie Bullnerd's last appearance before ChalkZone ended was "Teacher's Lounge." You think at first that it's just coincidental production order, but let's really look at this. In this episode, Reggie makes a "rude drawing" of Mr. Wilter and frames Rudy for it. After a series of events, Rudy manages to get Reggie's full name, which, as he puts it, is "the humiliating secret [he has] guarded [his] whole life." Rudy uses this to blackmail Reggie into admitting his guilt and get Rudy off the hook. All well and good if you're just getting out of detention for someone else's crime, but really think about this. This is a school bully who has given Rudy a bad time since he was eight years old! But now Rudy has learned a secret about him that made him whimper like a puppy dog. And he got something he wanted from him thanks to it. Sure, they had to sing the school anthem, which Rudy clearly wasn't enjoying, but that doesn't in any way squash the rare power Rudy has over the big jerk. There's no telling what else Rudy can do with Reggie with this power. If he wants the boy's lunch money, or threatens someone he cares about, like Penny, he'll just remind him of his full name. Never again would Rudy or his friends have to worry about being bullied by Reggie. Someone give this boy a medal!
In the beginning of Poison Pen Letter, Rudy is angry that Michelle Norwegiano didn't invite him to her party. Notice how, though clearly pissed, he doesn't take any action against her. Then he hears Penny wasn't invited either, prompting him to write the titular Poison Pen Letter. He's taking action not after he was wronged, but after his friend was wronged. He even says "I've had it" shortly after hearing Penny wasn't invited. It turns out they were invited after all, but still.
The premise of the show is that ChalkZone is a world where chalk drawings go and come to life after they are erased in the real world. This is fine and dandy until you consider that many episodes involved ChalkZone being endangered by a drawing of a monster, a natural disaster, or some other dangerous thing. It's also worth noting that Rudy and Penny never try to destroy the chalk creations if they are sentient beings. What if someone erased a chalk drawing of a serial killer or a rapist? What kind of horrific things would happen if those kinds of things existed in ChalkZone? Worst of all, how would Rudy, Penny, Snap, and the people of ChalkZone be able to handle such a situation?
The episode "That Sinking Feeling" begins with Reggie stealing Rudy last piece of magic chalk, which he says was his last piece. After a brief chase, Reggie just decides to smash the chalk to pieces. Luckily, Reggie grinding the chalk was enough to create a portal into ChalkZone, kicking off the plot of the episode, but really think about this. Rudy's last piece of magic chalk was stolen and nearly destroyed by the school bully. If he had just taken Penny's advice and went into ChalkZone at a safer place than out in the open, this could have been avoided. In that act of carelessness, never again would Rudy have been able to visit ChalkZone. Let that sink in for a moment.
Double Trouble has Skrawl and Craniac 4 attempt to destroy the Magic Chalk Mine and make Rudy their slave. They nearly succeed in wiping out all the magic chalk, and they were only foiled when Snap was able to alert Rudy in time. The question is, what would have happened if Skrawl and Craniac 4 had won? Rudy had a very real risk of being trapped in ChalkZone as a prisoner where he would not survive long as the chalk food and water would do nothing for him. Penny might be okay, but it is possible she would attempt to rescue Rudy. If that failed, she was in danger of being locked in ChalkZone along with Rudy. And that's not getting into the parents. What would have happened if they had found their children missing? There would be no trace of them left and they would be left not knowing what had happened to them. Not to mention that Rudy and Penny both had only 24 hours to get out of Chalk Zone since Word of God revealed that humans that spend more than 24 hours straight in Chalk Zone turn into Zoners. And since Zoners can't use chalk, if Rudy had turned, Skrawl and Craniac would have had no reason to keep him around...
The episode Chalk Queen is this trope in spades. The plot concerns Skrawl kidnapping Penny and convincing her to rule ChalkZone with him as his titular "Chalk Queen". Even ignoring the unsettling feelings things like this might implicate, this wouldn't be good for her in other aspects either. For one, it's previously established that humans cannot eat food (nor drink water) from ChalkZone. Unless Skrawl allowed her to take eating/sleeping breaks in the real world, she will most likely starve to death as the Chalk Queen. Another issue that arises from this is the fact that Penny's Chalk Queen antics nearly led to Snap burning alive in the volcanic salsa. And we know he would have burned to death—just ask her taster. Literally the only reason he didn't was because Rudy poured milk he drew into the salsa, neutralizing the acid. He had to act fast—on his last stub of chalk, no less! If he DIDN'T act as fast as he did, Snap very well could have died. Penny and Snap often butt heads with each other, but how do you think the former would feel about the latter's life being put at risk? The fact that she was faking all of this does little to soften the blow.
Even more unsettling is the fact that both Rudy and Snap forgave Penny almost instantly after the incident. Unless they had a chat later on about this, this is one of the most extreme cases of Easily Forgiven.
This becomes even creepier with the Word of Godreveal that if Penny really had been on Skrawl's side and stayed in ChalkZone, she would have turned into a zoner. I...think that counts as Body Horror.
In the TV Movie "The Big Blow Up", at one point Barney loses his body parts and is reduced to a, as Snap puts it, "babbling moron". While this does make for a couple funny scenes, it immediately becomes horrifying when you consider the implications of this. The fact that Barney becomes an idiot after losing his parts means that his own brain does not store a lot of information; it's spread through his body, and if just one part is removed, he immediately loses access to that portion of knowledge. And the more he loses, the worse he gets. As hinted by a quick scene later on, he has forgotten who Penny was for a while, meaning he can also lose knowledge of people that he meets. On top of that, his personality does not return to normal until he has at least one of his body parts reattached, meaning that even the core of who he is is affected by the body parts. So...what would happen if he were to lose a part permanently? Or if someone with the ability and nasty enough intentions were to mess with his internal data? This very nearly happens to him in the movie. It's scary enough that Barney did this despite not knowing what it would do, but all the parts spread out and it takes a great deal of effort to get them all back. What if he had done this when Rudy, Penny, and Snap weren't there? He would have been doomed to walk around aimlessly, unable to do anything or defend himself even until someone ate him. Suddenly, this makes his "babbling moron" scenes a whole lot less funny.
Probably one of the other reasons he lives in the nearly impenetrable forest away from anyone.
The episode with that woman who only liked realistic artwork takes on a horrid twist when you think about it. She was brought in by the school to teach the kids, all of whom are Rudy's age, and prior to Rudy driving her into a breakdown, was apparently well-thought of. Then she finds out one of her students, Rudy, prefers drawing cartoons. Unlike Mr. Wilter, who would just scold the kid and try to redirect him, she outright tortures Rudy into compliance. Which makes you realize...how many kids has she done this to before? And regardless of the number, unlike Rudy, none of them had access to Chalk Zone so they likely were broken permanently.
One can't help but wonder about the fate of the teddy bear being lowered into a volcano by a crane at the end of "Draw and Let Draw" after Rudy decides to stop jumping to conclusions and attempting to fix other people's sidewalk chalk drawings, since it's implied that the teddy actually was in danger.
Penny chastises Rudy for using a chalk-created machine as a science fair submission, as if he's cheating. But is he really? In this fictional universe, why wouldn't chalk magic count as science? It's a natural phenomenon that makes his machine work. Maybe it's not what you first think of as "science", and maybe it's not a field of science many people know about, but it's still science. If anything, Rudy is doing the opposite of cheating, by submitting something that really, legitimately is an extremely impressive application of science, and passing it off as something much less spectacular.