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.
Evil Is Sexy: Hilla wears bare minimum clothing and Orchid is dressed in an evil black uniform that borders on being a fetish outfit. Carta The Sea Witch also shows this in spades, not being so much evil as apathetic and disinterested in humans to the point she doesn't care if they're in trouble. Kyrin as well, as her motivations lean towards the selfish anti-hero end of things at times. And finally, let's not forget Empress Cygnus.
Fridge Horror: One quest requires you to "lighten" the floating island of Orbis by killing monsters. Unless those monsters really do disappear when they die as is shown in-game, that would mean their corpses are being dumped off the edge of the island to lighten it.
Why are the Pepe invading The mushroom's kingdom. You see, Pepe are native of El Nath which is slowly being destroyed by Zakum as well as King Von Leon. They are running for their lives and you are murdering them in cold blood.
Fridge Logic: The core plot of the Commerci area is that no one in Commerci is aware that anything exists beyond Dawnveil, but despite this, trade offices still sport maps of Victoria Island and Ossyria on the walls.
Game Breaker: In general, each new class Nexon brings out will at least start as a Game Breaker. As of the time of this writing, it will be Xenon and Demon Avenger. The pattern usually goes that a new class starts as a Game Breaker, receives some Nerfs a patch or two after, then receive buffs again in later patches (see: Mercedes, Demon Slayer).
In the past, there used to be a "world record" for a group of players on a server killing Zakum, the first of several bosses that used to require a raid of people to fight, in around two minutes. There is also a video of a newer class, the Angelic Buster, kill Zakum on her own in four seconds.
The Kaiser class has consistently remained one of the strongest classes with one of the highest, if not the highest DPS, being very mobile, fast attacking, powerful, and the ability to transform into Final Form for even more power, and to drive it home further, they receive a Hyper Skill at Level 200 that allows them to instantly transform into Final Form, AND ignore the nasty Damage Reflect to boot.
Good Bad Bugs: These have since been patched, but between the Bodyguards in Showa (Japan version only) and Bigfoot in Crimsonwood Keep, Maple Story programmers seem to be quite good at forgetting to make bosses unpoisonable. What makes the latter even more hilarious is that it was released alongside a new server which had a double EXP event. Cue the speed-leveling Fire/Poison Mages.
Due to some oddities with the physics engine, jumping while walking on certain slopes, or jumping while taking damage from spikes(typically the thorny plants in some areas) can send the player rocketing pretty fast in a super jump. Made useless by many classes getting double jump, though.
While many pots drastically cut in price at the main towns after Big Bang, the outskirt towns that had high healing or % pots, which are still very much expensive.
For that matter, many of the quest unlocked stores have absurdly high prices for common items.
Outside of big bang edits, there are a large number of forgotten towns, that routinely miss most updates of store or game function.
Love It or Hate It: The anime adaptation is this by fans, whether it is a good adaptation or not.
Memetic Badass: Due to being the former strongest boss in the game and being incredibly hard to defeat, while also still being pretty cute, many Maplers believe that Pink Bean may be the mutated son of Chuck Norris.
Most Annoying Sound: In Japanese MapleStory, if you successfully inflict a debuff with a Flare/Sphere Glaive, or using a certain pet equip's special debuff ability, a very annoying sound is played. It gets worse in huge boss parties when everyone has it.
Player Punch: In the Resistance storyline, Vita, the girl you rescued during the tutorial, turns out to be a Manchurian Agent programed by Gelimer. Then, when the player goes to rescue her, she's rigged to a bomb that will blow up if she tries to escape. Thus, in order to save the player, Vita forces the trap to explode before the player can even attempt to rescue her.
In the new Explorer storyline, not only does the Black Mage break free before you can attempt to fix the seal, but as retribution for trying to stop him, he attacks Maple Island.
Kill stealers were a big problem in previous years, when training spots were limited and ranged classes reigned supreme. Now, with the abundance of maps and places to train at, kill stealers are much harder to come by, however, they are still there, usually on the bandwagon for whatever powerful Game Breaker class was just released.
For a while, there was a group of people who would insult you for not following a specific build. If you didn't roll perfect stats at creation and stuck with it, or invested in skills that they don't recommend, they called you a bad player. The stats bit has lessened since the game gives you "perfect" stats automatically upon creation and you can choose to let the game auto-distribute your stats now, but they're still out there.
Possibly justified for clerics and archers, where the game balance actually screws them over. Clerics can now deal more damage if they have decent weapons, true, but chairs are completely useless for restoring needed MP points (when before MP Restore would have renewed in conjunction with MP Eater in battle). Hence, the prevalence of pots dropped by enemies. In the latter case, there is an accuracy equation based on levels rather than stats (which would be okay if it only allowed you to hit things at lower levels, but it also prevents training at twenty levels higher (so, no boss runs with archers).
The maze forest near NLC now has a different system, making the already confusing maps in some guide websites like Hidden Street useless.
What maze? As of the NLC alteration from the alien invasion, the maze is gone. The entire Crimsonwood area is now just a flat stretch of a few maps. No maze, no instant death jumping puzzles.