We live in Santa Martina, remember? This town is full of wackos.
Sammy Keyes and the Psycho Kitty Queen
Sammy Keyes, to quote The Other Wiki, is a series of mystery novels aimed at children and teenagers that, of course, follows the adventures of the titular protagonist. In most of the books, she deals with everyday junior high school life, solves mysteries, and contends with her arch-nemesis Heather Acosta, though there have been a couple of exceptions to the formula.
These works contain examples of the following tropes:
Adult Fear: One story centers around Sammy running into a scared, desperate girl, who forces Sammy to take a bag. When the girl is forced to leave, it turns out that there's a baby inside. It's later revealed that the baby was the girl's son and that she was forced to give him to a complete stranger to protect him from her abusive ex-boyfriend, who was hunting her down. The climax of the novel reveals that the ex did catch her, and left her in his basement, tied up and starving. After she's rescued, she wants to see her baby before getting medical treatment.
An Aesop: Most of the books have at least one. Despite being Anvilicious at points, they're handled well.
Author Appeal: Van Draanen's parents are Dutch immigrants, and so are Dot's. Her husband's great-grandfather crossed the plains in 1850. In Moustache Mary, the eponymous pioneer was part of a group of travelers doing the same thing, and Sammy spends New Years' with Dot's family. It's one of the few cases where the authour appeal is educational-as well as delicious.
Comic Book Time: The first installments were published, and presumably set, around 1990ish. About a year and a half has passed in Sammy's world, but the setting has kept pace with the twenty-some years passing on the outside: in recent books, most middle-school kids have their own cell phones.
More recently, Van Draanen said on her blog that Sammy will find out who he is with in the next few books, and the series will continue for several books after that. At the time of this edit, that book and a second came out; only one more is planned.
Enemy Mine: Sammy and Officer Borsch help each other out occasionally. They eventually become Friendly Enemies, and then outright friends.
Kick the Dog: Heather's character is practically built upon petty maliciousness. Special mention goes to her taunting Sammy about losing her father's softball mitt in Sisters of Mercy.
Kid Detective: Sammy herself, sometimes with help from her friends. She calls it "snooping".
Masked Luchador: El Gato in Psycho Kitty Queen. He's actually Borsch, undercover on his own time to infiltrate a catfighting ring.
Mystery Magnet: A stranger example than others, as each mystery usually takes place within a month. Other Mystery Magnet stories aren't as regulated.
The Nicknamer: Sammy, in regards to practically everything. She has a tendency to give people she encounters (often unflattering) nicknames before she knows their real names. If she likes you, she'll start calling you by your real name once she knows it, but if not, the nickname sticks.
Not Allowed to Grow Up: Averted. Sammy's age progresses as the series goes on. At least, until Psycho Kitty Queen, when Lana reveals she lied about Sammy's age to get her into Kindergarten early. And she tells her this days before her 14th birthday, which is actually her 13th.
One Steve Limit: Cassie Kuo, a minor character from Sisters of Mercy, is given the nickname "Cricket" in Wild Things, apparently so as not to confuse her with Casey Acosta.
Out, Damned Spot!: Happens in Sammy Keyes and the Dead Giveaway. Luckily, it ends better than a lot of examples.
Parental Abandonment: Sammy's dad has vanished, and her mother has run off to Hollywood to be an actress.
Casey certainly believes this is the case in The Wedding Crasher when his dad Warren gets a part in the same soap opera as Sammy's mom, thus forcing him to move in with his mother and sister, both of whom he hates. This causes some angst in his relationship with Sammy. It's also on the Squick side of things for the both of them when they find out that Warren and Lana are moving in together after having dated for a while.
Together in Death: Really, really creepy variation in Sammy Keyes and the Hollywood Mummy. Sammy's mother Lana, an actress, fakes an ID so she can claim to be 25. Unfortunately, her new birthdate is the day her boss's wife died. He thinks Lana is the reincarnation of his wife, and he tries to kill both of them so they can be reincarnated together.
Villainous Breakdown: In the later books, this happens to Heather. She still hasn't really recovered from it. It doesn't help that Sammy saved her from drowning, either.
Wham Episode: "Showdown in Sin City." Grams and Hudson get married, Marissa's family falls apart and decides to move away from Santa Martina, Sammy and Heather team up and overcome their mutual hatred, and Sammy's father's identity is revealed.