Wanda in the "Magic School Bus Holiday Special" reveals that she's eager to donate an old toy soldier she's had since childhood to both make another kid happy and to see The Nutcracker. It seems odd that she wouldn't give it to her brother William. The construction episode reveals that he is a slightly destructive toddler. Seeing how upset Wanda was when her toy was recycled, of course she wouldn't want her baby brother to smash it. note Most toys of that nature aren't recommended for kids under the age of three, anyway.
As for the special itself, it makes perfect sense for the topic du jour to be recycling, because like the holidays, it's hoped that recycling is something people will keep coming back to, and now we get to recycle the special every year.
The Acceptable Breaks from Reality in "Gets Programmed" make sense in-universe. Mikey doesn't read the program back the way it was actually written, he read back what the results were because he knows that the others would not understand it. He doesn't understand specifically how a computer works, but he knows about how to program them.
This also makes for an extra case of Fridge Brilliance as to why he would be willing to learn how a computer works - because he wasn't taught that bit, only how to write programs. If he wants to get about to actually building computers, you have to know these things.
In the beginning of "Ups and Downs", we know Wanda's mother is a science journalist, and she's the one who initially calls out Gerri Poveri as someone who would do anything for a story, even if it means making it up, and she sounds very certain about this. Professional opinion of someone else's reporting habits? (Maybe she's even dealt with Gerri professionally before, enough to form an opinion about her ethics.)
In the first episode, Arnold is willing to pull off his helmet on Pluto just to prove a point to Janet despite fully knowing that he will pretty much die of freezing. So why did he become a coward while wishing for normal field trips in the rest of the series? He is likely suffering from PTSD due to his Near-Death Experience and is hoping he doesn't have to pull a stunt like this a second time!!
The female producer is shown eating Chinese takeout in the "Producer's Segment" of "For Lunch". Stereotype, right, since she's Asian? Well, actually - she's at her desk. Chinese takeout containers are known for being easy to eat out of at a desk or on the street, and for being much more of a "meal" than a sandwich. Plus, it's very easily recognisable and takes much longer to eat than a sandwich. She also might have it in the fridge - Chinese takeout leftovers are common "office food".
The male producer in "Revs up" says "Why didn't I think of that?" when it was asked why he didn't just use gum to cover the sparkplugs or flood the gas tank. Because gum getting in the tank or over the spark plug would be much more deliberate than Peanut butter, which is stated to have been there by accident. Plus, Mr. Junkit is shown as using a lot of peanut butter. A lot - the only way he would be able to cause that much damage with gum would require way too much!
The kids' intervention with peanut butter in the gas tank also makes sense - gas dissolves peanut butter, but it takes about half an hour.
In "Inside Ralphie", just what does Ralphie have? His main symptom is a sore throat, which is usually caused by a cold or the flu. But the infection is shown to be caused by bacteria, which are destroyed by the medicine his mother gives him; colds and flu are viral, and the medicines used to treat them can't kill the virus, they just relieve the symptoms. Still, there's another common childhood illness that causes a sore throat and a fever, which could be what Ralphie has: Strep Throat, which is caused by a bacteria. So Ralphie's mom giving him something to kill the bacteria isn't actually bad writing.
Arnold's head turned into a block of ice on Pluto, so that Janet had to carry his stiff frozen body onto the bus. Just what did Ms. Frizzle do either on Earth or on the bus to heal him mostly so that he only had a cold?
In the "All Dried Up" episode, did their parents even know that their kids would be gone overnight?
Going on that, Arnold in "The Magic School Bus in the Haunted House" mentions that they got permission slips to spend the night, but that the slips didn't mention "haunted houses". So just how often does Ms. Frizzle remember to include that?
In "Butterfly and the Bog Beast" just how would Janet have reacted if she had realized that the butterfly she caught and planned to feed to the "bog beast" was actually the class shrunken and changed into a butterfly? (The class leaves that bit out when they finally change back and pick up Janet from where she's fallen in the mud.) If the bog beast had been a real thing and not actually just a butterfly with bright coloring, Janet could have easily fed her own cousin to it. Janet may be a Jerkass but she freaked out when Arnold took off his helmet on Pluto for her, knowing it was her fault that he made that decision. How would she have lived with the guilt that her own bullying and greed led to several students and an adult dying?
More Janet horror, by implication than anything else. In "Lost in Space", Arnold's response to Janet insulting Miss Frizzle is to go into Tranquil Fury mode and go out of his way to prove that no one is better than his teacher. Flash forward to the episode with the "theater ghost" that turns out to be Janet screwing with the rest of the class for kicks. Despite the fact that he's clearly not happy about being used to scare his friends, Arnold is unable to get out of helping Janet until the rest of the class turns the tables on her. What exactly did she do to him to brow beat him that badly?
In the episode about the city and the animals living in it, it's implied that this was done on a whim - meaning their parents would easily not know where they are, only that they are late getting home.
In Out of This World, the bus deflects an asteroid by increasing its own size so that its gravity will change its orbit. The sudden appearance of an object the size of the moon in Earth's orbit would cause major problems (i.e. tides going out of whack) just by being there. Nice Job Breaking It, Herodoesn't even begin to cover it.
Janet's manipulation talents get particularly horrifying when you realize that despite the fact that she does care about Arnold, she's perfectly willing to use him in schemes to bully said friends (the "ghost in the theater kidnapped Arnold" scheme in the light episode comes to mind) or turn not just him but the entire class against one of their own just on a whim (when she suggested Phoebe was sabotaging the soccer team because they were playing her old school in the butterfly episode). This tendency is worrying not just for her but for everyone around her, to say nothing about what it implies about her parents and how they raised her.
Their single appearance in "Lost in the Solar System" implies that they're so used to Janet's crap that they just ignore it.
These kids' lives are going to be seriously depressing once they graduate Ms. Frizzle's class. Imagine having to go through a normal classroom education after all those wild adventures. Nothing will ever seem as exciting again.
Perhaps not quite so horrifying. In "In the Arctic", Arnold has a run in with a kid from the grade above them. Though he seemed to glare at Arnold before their trip to the aforementioned Arctic, the kid reveals that he was actually a part of Miss Frizzle's class the year before, and talks quite fondly about lessons from her class when he notices Arnold's thermal cup cover. It's more than likely that the kids will be able to move on from Miss Frizzle's class with only fond memories of the adventures they had, and not regret that they aren't there any longer. As others before them have done.
The Magic School Bus Rides Again takes place in the next school year, and their still in Miss Frizzle's class, albeit a different Miss Frizzle.
In Inside Ralphie, until the medicine that his mom gave him kicks in, Ralphie's immune system is losing the battle against whatever bacteria infected him. How much worse could it have gotten if his body continued to be overwhelmed?
Not that much worse, considering your point isn't even implied. We only see bacteria overwhelming the one blood vessel the kids were in, and there's no reason to think that scenario was everywhere.
If the Wild Mass Guess that Ralphie has strep throat is true, though, then without the medicine it could have been much worse – it might have turned to scarlet fever or some other serious complication. Ralphie is lucky that he lives in the era of antibiotics.
