Accidental Innuendo: Tweak's name is a bit reminiscent of "tweaking" (which means getting high).
Adaptation Displacement: The animated adaptation has heavily eclipsed the book version in popularity.
Broken Base: The heavy use of Green Aesop in Above and Beyond is contentious to older viewers; some like that it addresses climate change and wish that it went further by addressing its causes, while others find it repetitive that so many episodes are based around rising temperatures and water levels. And then you have climate deniers who find it annoying for their own personal reasons.
Shellington being autistic is a particularly common fan theory, due to his tendency to fixate on certain things.
Another frequently headcanon is Kwazii having ADHD, mainly attributed to his short attention span, impulsivity, and other hyperactive tendencies including his flips and “yeow!”s.
Fridge Horror: If Boris was not there to break through the ice and save the Octonauts, then who knows what could have happened?
In the best of cases, another creature would saved them. In the worse of cases, they would be died from hunger and frozen.
The show is pretty popular in China, so much that Season 5 showcases numerous sea creatures commonly found in China. There's even an Octonauts area at a popular theme park in Shanghai.
It's also popular in North America, thanks to its critical acclaim in the country and it airing on Disney Junior.
The episode with the Narwhal. The Octopod is constantly freezing, and it loses power. Then it just keeps freezing and then after the ice avalanche scene, when Barnacles leaves the Octopod, the Octopod looks really weird and pale and covered in ice, it also has a weird mix of grayish-orange as the Octopod's color. But to soften the blow, it has a few funny moments.
In the Season 4 special: Operation Deep Freeze, Oojo falls off a cliff. Twice.
Characters almost suffocating/drowning pops up a lot more than you would expect for this happy-go-lucky preschool show.
In the Giant Comb Jellyfish, after get free from inside the jellyfish, Peso is lost and being chased by a hungry great white shark who is a non talking character like the one that appeared in "The great white shark" episode, and looks more like a ruthless predator. He was so luck that the giant jellyfish was here again, because he was almost eaten alive by the shark, without many probalities that the Octonauts will find he was eaten. Or Fridge Horror, imagine if The Octonauts track Peso by his implant and only finding shark poop. That could be devastating for them. Seriously, Peso was so lucky.
In "The Siphonophore", the titular creature can come off as Unintentional Uncanny Valley to some people, especially their Hive Mind behaviour, Creepy Monotone voices and the fact that they tried to eat Kwazii and Dashi.
Not to mention that this is the only episode where there's an implied Family-Unfriendly Death. Earlier in the episode, Shellington explains that if the siphonophore goes any higher than the Octopod, it'll explode.
Periphery Demographic: Teens and adults love this series just as much as kids because of its soft artstyle, fun characters, and abundance of science facts.
Seasonal Rot: As the seasons go on, the "Creature Report" segments degrade in quality with each one produced, namely in lazier lyrics, more episode-specific notes added in instead of more creature facts, and Barnacles' singing voice sounding less like the stock audio.
Signature Scene: The infamous "YOU'RE STANDING ON MY FOOT!" scene from "The Narwhal".
Spiritual Successor: Some see this series as one to The Save-Ums! due to having chibi-esque characters with bulbous heads and a crew of small, unintelligible critters on board with the team.
Trans Audience Interpretation: Most fans subscribe to the idea of Kwazii being trans after an error in one of the original books where he is referred to with female pronouns went viral.
Books
Nightmare Fuel: The Shade Forest, while not so bad for older readers, can be scary a little for children, with the spiny, twisted branches, the tooth-filled predatory plant at the top and the monstrous shadow bats flying above it
Also, the sunken city in "The Great Ghost Reef", while not that bad, crosses with Fridge Horror, since, if there is a city, that is implied not have been built by the sea creatures (Well, how could they, after all?), so...where are the dwellers?
Also, From the same book, the ghostly-figures that haunts the flooded city, while not be horrifying for adults and some kids, are unsettling if you are not prepared to that in a child-friendly book series like that
In "The Only Lonely Monster", as Tweak shows her ability to glow in the dark...somehow, a transparent, elongated rabbit-wraith materializes in the corner of the picture, while being Night Mare Retardant if you look to its silly face and cartoonish appearance, is wierd. Just, who is that guy, and what wants with her?
