* DemonicSpiders: Slithers are sometimes this, sometimes just GoddamnBats. A more traditional example would be the spider Darkling that spews a bunch of tiny spiders when it gets hit with Resplendently Scintillating Illustrations.
* FoeYay: Dess and Melissa.
* FridgeLogic: Given the series relies heavily on a base-10 numbering system and comparatively new ideas (such as latitude and longitude), there's a lot, but [[MST3KMantra it doesn't really take away from the fact that it's still a pretty well-written YA series]].
* GameBreaker: Essentially the [[spoiler: Flame Bringer power. Technology, electricity, and fire aren't supposed to work during Midnight, even if a Midnighter touches it. Unless they're a Flame Bringer, like Jessica, who can break that rule on a grand scale. She can also give 13-letter names to much larger objects than the others. Which means even though Jessica was completely useless for most of the first book, in the second and third she can kick some ''serious'' Slither and Darkling ass. "The all-powerful Flashlight Bringer" indeed.]]
* GoddamnedBats: Slithers often straddle the line between this and DemonicSpiders.
* [[HoYay Les Yay]]: Sometimes between Jess and Dess.
* UncannyValley: Stiffs