These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Also the music from Maze Madness. Levels 21-25 have a really cool pirate theme. Listen to it here.
Demonic Spiders: Water Worries may be really easy, but that doesn't stop the jellyfish from being way more annoying than they need to be. They come out of red bubbles like all the other enemies, and they will happily block any ammo that happens to cross them. They also descend incredibly slowly and if you happen to run into them, they shock Luther an make him unable to use his ammo unless you get Percival to drop a bowling ball on him. As if that weren't enough, if you are one who likes to shoot everything in sight, you're going to get many of them on the screen at once, and they will make the level a whole lot more painful to play than it needs to be. And they're only the second enemy in the game.
Moral Event Horizon: Averted. In "Eddie Eats Luther", Freddi seemingly crosses it when she feeds her friend Luther to Eddie the electric eel. Of course, that was just her imagining this. It was also non-canon to the game.
Also if you use the Junior Helper in both games then Maze Madness qualifies as well.
Most Annoying Sound: In ABCs Under the Sea, Freddi and Luther's voice clips can get pretty repetitive, at least if you aren't part of the game's target audience. They can be quieted or muted, but only along with the other sound effects.
Pandering to the Base: The series was originally based around problem solving with several educational values buried within the gameplay and several humorous moments, making it fun for kids and adults. Nearly a decade after Atari's buy-out, they got 1st Playable Productions to create ABCs Under the Sea, a game based around learning about letters, words, numbers, directions, and colors. What the heck. And despite this, the game tries to ride on the previous installments' success by pointing out that it's from the award-winning series with 15 million copies sold worldwide...not mentioning that the rest of the series was made by different people. (Additionally, one of the game's alternate titles is ABC's Under the Sea, which is grammatically incorrect.)
Unfortunate Implications: In the British dub of Hogfish Rustlers of Briny Gulch, almost all the characters have American accents! (except Freddi and Luther) Even those who weren't even Western, like the pufferfish.
Viewer Gender Confusion: Quite a few didn't know Freddi was a girl until they played the fourth game, where her gender gets uttered at the very beginning. It doesn't help that she was called a guy at the end of the first game. Her gender can be determined as early as the second game, though, when the player gives Mr. Triplefin his business card. Mr. Triplefin called the two of them boys, at which Freddi corrects him that she is a girl.