The Ace: One book's plot is essentially about an Ace showing up: somebody who (by Everyone Looks Sexier If French) is prettier than Angeline, more vicious and destructive than Isabella, and more spontaneously artistic than Jamie. She eventually turns out to be a legendary outcast who rendered her school uninhabitable in a desperate gamble to go somewhere nobody had heard of her and make friends.
Alpha Bitch: Angeline... according to Jamie, anyway. Of course, she has no clique, hangers-on or regular friends (until you can count Jamie), is friendly to all the school "losers", shows no concern over her social status, and while an excellent manipulator, uses said power rarely and generally "for good".
Beautiful All Along: Parodied on two separate occasions. The first time, Jamie and Isabella give a makeover to an unpopular girl named Margaret and as a result, end up becoming Unwitting Pawns in another girl's plan. The second time, it turns out that the only reason Jamie isn't considered pretty is her unflattering hairstyle.
Chekhov's Gun: Being surprisingly tightly plotted is one of the strong points of the series. It's a good bet that everything is one, and trying to figure out just how some offhand comment or minor event is going to recur and become a plot element is a good part of the appeal to adults.
Epic Fail: In one book, Jamie, Isabella, Mike Pinsetti and TUKWNIFnote "that ugly kid whose name I forget" are put into a group in gym where they are given an assignment to get a plastic baby across the gym using a rubber snake, a shoe, and a pot without it or them touching the floor (throwing it isn't allowed). Their plan is to use the snake as a catapult to launch the baby across the gym. Sounds good, right? Wrong, oh so horribly wrong. Isabella's aim is thrown off due to her new contact lenses and she launches it in the wrong direction. Pinsetti, who is supposed to catch the baby from across the other end of the gym, ducks on instinct ("a month of head injuries had him spooked") and the baby sails through the window, falls onto the asphalt, and gets run over by a school bus.
Exact Words: When the gym teacher says each group needs to get a plastic baby across the gym without them touching the floor and throwing the baby is not allowed, Isabella uses the rubber snake they've been given to launch the baby instead.
Getting Crap Past the Radar: This is a literary form of family entertainment, meaning it's good to read to kids and won't bore the reader.
Global Ignorance: "Wheretheheckistan", Jamie's catch-all term for any foreign country she is unfamiliar with.
Insane Troll Logic: Jamie's thought processes sometimes follow this pattern. Example: She sees Angeline with two younger girls who don't look like her. Obviously, they must be siblings, but they don't look like Angeline, which means Angeline's father did plastic surgery on her, which means Angeline is rich. Tadah!
In much quieter (but equally effective) fashion, Assistant Principal Devon and his niece Angeline have their moments.
Meaningful Echo: The line "The first rule of the road is that beautiful things take time, and you can't rush glue" in Never Underestimate Your Dumbness.
Men Can't Keep House: Jamie's father comes up with 'creative' ways to avoid dirtying any dishes when his wife is away and does not know how to use a washing machine (or even what the machine to clean clothes is called) and jokes that if he hadn't met Jamie's mother he would be living in a very dirty cardboard box.
Mind Control: In two books, some way to control people's emotions and attitudes through scents is plot-significant, and seems to go a bit beyond Jamie's fertile imagination. A common early example of Jamie's imagination is her momentarily falling under Angeline's "evil spells", with descriptions almost bordering on self-Foe Yay.
"I don't want to say she's still eating a lot of pencils, but when she farts, I swear you can almost see a little puff of sawdust."
Parody Sue: Angeline, though the sixth book shows that she could also be considered a Deconstructed Sue. The first couple of books may be one of the more complete subversions of the Canon Sue trope in literature. Jamie starts out obsessing about how Angeline is so obviously a Mary Sue (not by trope name) and how every little thing that happens is clearly all about Angeline. In fact, Angeline's only real relevance in the early plots is actually caused by this obsession. She only has the narrative spotlight because the protagonist is constantly throwing it at her.
Pooled Funds: At one point in the second book, Jamie imagines Angeline taking a bath in pure money, complete with hot and cold running diamonds, jewel encrusted soap and a "rug of extraordinary fluffiness".
Eventually, Hudson to Isabella. This is even portrayed in the ninth book with several similes.
Suddenly Always Knew That: Almost a Running Gag. At the end of a book where a skill is plot-relevant (speaking a foreign language, playing guitar in a band, maintaining an automobile), it tends to turn out that Angeline had said skill the whole time and didn't bother to mention it.
Take That: The Whisker Brothers, a three-boy band whose lyrics seems manufactured to make a middle school girl like them. Sounds like The Jonas Brothers.
Toilet Humour: Recurs. In particular, Jamie's dog Stinker is a magnet for this type of joke. As often as not, Stinker's bodily functions even drive the plot.
Token Evil Teammate: Isabella has no trace of empathy and a very utilitarian concept of friendship. In fact, it's safer not to be her friend because — well, it's safest not to be anywhere near her. She is still unquestionably a True Companion.