Cult Classic: Dragon Quest, despite being the seminal JRPGs, wasn't really able to gain a foothold in America during the 90s. It fared much better during the revival in the oughties, but not enough to convince Square Enix to continue localizing much past IX and the remake of VI, which were only even released outside Japan because Nintendo put in the effort to. It wouldn't be until Heroes that Square Enix started localizing the games again, and some of them such as the remakes of VII and VIII only happened thanks to Nintendo once again handling publishing duties.
Demonic Spiders: Lots of examples, particularly enemies that are immune to magic, can One-Hit Kill you, cast Sleep, Healmore/Midheal, and/or Hurtmore/Firebane/Sizzle (Wizards), inflict poison or other Standard Status Effects, and have high defense or speed stats (which makes them dodge and block you a lot, eg Demon Knights).
Germans Love David Hasselhoff: The biggest fanbase in the Western Dragon Quest community appears to be in France, as it was the French fanbase that ultimately got Square Enix to release the 3DS remake of Dragon Quest VII worldwide.
Hell Is That Noise: The little ditty that plays when you've equipped a cursed item that overrides the current music and comes at you so suddenly that it's entirely capable of making you jump out of your boots.
And much worse, this horrible noise is also played after your save file is DELETED in 16bit era games, because the games were designed to delete "corrupted" save files at boot-up. Needless to say, this sound has traumatized many players in Japan.
Dragon Quest V features monster catching and predated Pokémon by a good three years. However it's pretty undeniable that the Dragon Quest Monsters series was created due to Pokémon.
The concept of Psyching characters up to deal more damage actually started in Dragon Quest VII, but it was only used via special moves, and there was only 1 level of tension. Dragon Quest VIII greatly expanded on the idea and now tension is a core part of all Dragon Quest games, including spin-offs.
Pop Culture Holiday: An unusual case where the holiday changes with its observance. Dragon Quest games are known for releasing on Saturdays, so when a new installment comes out, playing and talking about Dragon Quest is made into a weekend event.
Porting Disaster: The general opinion of the mobile ports of the first three games. A lot of the monster sprites are Off-Model or lazily put together, the tile work is rather grating to look at and the most of the problems with the games from the original are still present.
That One Attack: Whack spells, in all the games they appear in. Spells that are reliant on RNG in general get this due to the enemy AI abusing it, but Whack spells are especially dreaded because they can instantly kill party members in a series where revival spells are also dependent on RNG luck. If you're especially unlucky, you might end up wasting turns trying to revive your party members while there's an enemy casting Whack (or worse, its deadlier version Thwack) spells again and again.
Woolseyism: The games released since Dragon Quest 8 have actually been blessed with a remarkably coherent localization, but contrary to popular belief the Hurricane of Puns, Added Alliterative Appeal, and general silliness of the franchise are actually taken from the Japanese originals (though sometimes rather heavily re-contextualized in service of trying to make the experience cohesive in the new language, the end result of which can be hit or miss, sometimes, depending on the player).