Characters: The Baby-Sitters Club
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- Bratty Teenage Daughter: All of them have several moments of this.
- Friend to All Children: Obviously, they love their babysitting job because they love kids.
- Heterosexual Life-Partners: Each pair of best friends: Kristy and Mary Anne, Claudia and Stacey, Dawn and Mary Anne, Jessi and Mallory.
- Jerkass Ball: They are portrayed as very nice girls most of the time, but all of them have their bitchy moments, and, depending on the book, they can Take A Level In Jerkass for the sake of the plot (arguably Mallory and Jessi less so than the others).
- True Companions: No matter what happens, the girls are there for each other.
- Wise Beyond Their Years: All these thirteen-year-old girls seem way too mature for their age.
Kristin Amanda ThomasKnown informally as Kristy, and rarely called anything else. Founded the club in the first book Kristy's Great Idea, and became the President, renowned for having an endless stream of "great ideas" (including the Kid-Kits, and many one-off events such as the Mother's Day Surprise, the various day camps they ran, and so on). Her father ran out on the family when she was very young, and in Kristy's Big Day, her mother got remarried to a "real live millionaire", Watson Brewer. Tomboyish and sporty, Kristy founded a kid's softball team for many of their sitting charges in Kristy and the Walking Disaster. In later books, she had a bit of a romance with the coach of the Krushers' rival team, Bart of Bart's Bashers.
- Academic Athlete: Kristy has the management skills to create the club and be its president. Her sport is softball and she even starts a kids' team. She's also a good student; in Kristy's Big Day, it's noted that she consistently earns straight As.
- A-Cup Angst: Kristy is the only 8th grade BSC member to not wear a bra and sometimes feels bad about it.
- Ambiguously Gay: Some fans suspect that Kristy fits this trope. She could occasionally be persuaded to wear a dress, and did have an on-off "boyfriend" named Bart, but never seemed to take as much of an interest in him as the other girls did with their own boyfriends (then finally broke up with him.) And in the movie, as The Nostalgia Chick noted, there's what can only be described as a Longing Look between her and Claudia.
- Brainy Brunette: Kristy has brown hair and is a very intelligent, driven young girl.
- Brutal Honesty: Lampshaded by other characters and even Kristy herself since the very first book. It sometimes causes a bit of problems between Kristy and her friends, who tend to get annoyed by her tactless ways.
- Control Freak: Kristy's organization and strong personality allow the club to run smoothly and let the girls accomplish many things that pre-teen girls would often find difficult. On the other hand, she can sometimes run too tight a ship — she has a special glare for members who show up one minute late to a club meeting!
- Cool Big Sis: Is seen this way by her stepsister Karen.
- Daddy's Girl: Both her biological father and stepfather seem to favor her over her brothers, although in the first case it's probably because she's the only girl and in the latter case, it's because she took the longest to warm up to him. It also could be a bit of skewed perspective because she's the main character.
- Death Glare: Kristy's "Look"
- Disappeared Dad: Kristy's father, Patrick Thomas, abandoned his wife and four children and almost never calls or writes.
- Girl Next Door: The Tomboy version.
- Hot-Blooded: Often loud and impulsive, with many power-hungry tendencies.
- I'm Not Pretty: "I don't think I'm as pretty as Mary Anne."
- Jerk with a Heart of Gold: Often seen as a bossy Control Freak but, while her flaws can get annoying, Kristy is a nice person who loves children and cares about her friends.
- Limited Wardrobe: Her "uniform".
- Kendo Team Captain: Of the Krushers.
- Massive Numbered Siblings: After her mother remarries and adopts a baby with her second husband, the Brewer-Thomas family fits this trope, though a blended version of it.
- Middle Child Syndrome: She's too young to hang out with her high school age brothers and too old to play with elementary- and preschool age brother, sister, and stepsiblings. It's not extreme — Sam and Charlie do invite her to play contact sports with them, and the kids are happy to include her in their games — but there's a still a sense of not quite belonging.
- Only Known by Their Nickname: In most books, identified only as "Kristy".
- Outdoorsy Gal: Possibly overlapping with I Have Brothers, who all share her enthusiasm for baseball.
- Outnumbered Sibling: As she points out in Kristy and the Mother's Day Surprise, it's her against three brothers. After her mom gets married, it's her and Karen against four brothers. Emily Michelle, her adopted sister, evens it up a bit more.
- Passionate Sports Girl: Kristy loves sports, and even coaches a softball team for small children. She calls them Kristy's Krushers, and it includes many of the club's sitting charges.
- Real Women Don't Wear Dresses: Kristy in the film says that she felt like a pencil when she was wearing a dress her dad bought for her.
- Rags to Riches: Via her mother's second marriage. It changes very little about Kristy herself, though.
- Tomboy: Justified, due to her growing up with three brothers and no female siblings.
- Tomboy and Girly Girl: Tomboy to Mary Anne's Girly Girl. She's a loud and bossy Passionate Sports Girl who couldn't care less about clothes and boys.
- Tomboyish Ponytail: Her default in official art
- Tomboy with a Girly Streak: Much more well-rounded about her tomboyishness pre-ghostwriter, she loved the bridesmaid dress for her Mom's wedding, wore skirts to school, likes babysitting (traditionally feminine), and proclaimed beauty contests to be fun despite sexist.
- Tomboyish Baseball Cap: On book covers, Kristy is always seen wearing baseball caps or visors. Softball is her fave sport.
Claudia Lynn KishiVice-president of the club, by virtue of being the only one with her own private phone line. Additionally, her junk food habit meant that she always had snacks stashed in her bedroom that the other girls could eat during their meetings. Artistic, flighty, and hopeless at school, Claudia defied the "model minority" stereotype to an extent. Her family was very conservative, and she often felt as though she was being compared unfavorably to her genius older sister, Janine. She had many casual boyfriends, but few serious ones. In Claudia Kishi, Middle School Dropout, she was pushed back to the seventh grade, only to be returned to the eighth grade with her friends in Claudia Makes Up Her Mind.
- Annoying Younger Sibling: Sometimes to Janine, particularly in early books.
- Asian Airhead: Early books treated this very mildly; later books made her seem almost borderline developmentally delayed.
- Big Eater: She is a model-thin junk food addict.
- Book Dumb: She's hopeless at school, hates math, and has serious spelling problems.
- Deadpan Snarker: Or as close as the BSC ever gets.Stacey: [The local department store] lost their Santa Claus.
Claudia: Disappeared between men's shoes and kitchenware, huh? I know that area. It's like the Bermuda Triangle.
- The Fashionista: Claudia is very creative and loves both fashion and art. She makes a lot of her own outfits and jewelry.
- Foolish Sibling, Responsible Sibling: The foolish to Janine's responsible.
- Generation Xerox: In one book, Claudia is shown pictures of her beloved grandmother Mimi as a teenager, and the resemblance is so strong that "we could have been twins."
- The Glorious War of Sisterly Rivalry: With Janine. She is "the pretty one".
- Hair Decorations: She loves them.
- Hormone-Addled Teenager: Like her best friend Stacey, she's very boy crazy.
- Informed Ability:
- Her artistic talent, which - due to the medium - is rarely shown.
- She's supposed to have a "cool" fashion sense and style but, based on the descriptions, most of her outfits seem just ridiculous.
- Like Goes with Like: In one of the Super Specials, there's a Japanese boy introduced solely to be a love interest for Claudia because she's Japanese-American.
- Popular Is Dumb: Like Stacey, she's quite popular at school. Contrasting with her sister’s Intelligence Equals Isolation.
- Self-Deprecation: Tends to be very insecure about her lack of book smarts, especially in comparison with her sister. Sometimes she mocks herself for it.
- Sibling Yin-Yang: With Janine.
- Sweet Tooth: She hides junk food all over her bedroom (and always shares it with her friends).
- The Unfavorite: She sees herself as this compared to her Teen Genius older sister Janine, while Janine feels the same compared to pretty, popular Claudia.
Mary Anne Spier
Mary Anne SpierThe secretary of the club, as she is extremely organized and had very neat handwriting. Was raised by her father, her mother having passed away when she was very young. In early books, her father Richard was very strict, but he gradually loosens up as time passes. She was Kristy's next-door neighbor before Kristy's move, and throughout most of the books is her Shrinking Violet best friend. She was the first of the club members to have a steady boyfriend, club associate officer Logan Bruno, whom she meets in Logan Likes Mary Anne. Becomes stepsisters with Dawn in Mary Anne and the Great Romance.
- Author Avatar: Ann M Martin identified her as such.
- Beware the Nice Ones: Mary Anne is very sweet and shy but...
- Beware the Quiet Ones: ...she gets extremely vindictive when pushed too far.
- Bitch in Sheep's Clothing: Not always, but she comes off as this in some books.
- Brainy Brunette: She's a good student and has brown hair.
- Daddy's Girl: She wasn't very happy about it at first, as her father was always overprotective, but they become much closer over the years.
- Fragile Flower: Mary Anne is so sensitive she'll cry at long-distance telephone commercials.
- Girl Next Door: Like Kristy, Mary Anne is a fairly normal, down-to-earth and pretty girl. In contrast to Claudia, Stacey, and Dawn who are all described as unique, trendy (Claudia and Stacey) and gorgeous.
- Girlish Pigtails: In the early books, which leads us to...
- Important Haircut: Her friends do not take it well.
- I Can't Believe a Guy Like You Would Notice Me: Towards Logan.
- Kindhearted Cat Lover: Her beloved kitten, Tigger.
- Missing Mom: Mary Anne's mother died of cancer when she was very little.
- Naïve Everygirl: She's very insecure, vulnerable, can barely talk to strangers, and is surprised when a cute boy like Logan actually likes her back.
- Official Couple: With Logan.
- Overprotective Dad: She has one.
- Romantic Two-Girl Friendship: With Kristy.
- Shrinking Violet: Her defining trait. Often other characters point out the differences between her and Kristy: Shy, quiet Mary Anne is the polar opposite of loud and outspoken Kristy, but they are still best friends.
- The Snark Knight: For the one later Flanderized as the sweet, sensitive one, Mary Anne sure releases the snark sometimes:Her "apology" note to Kristy after the girls fight in Book #2 (to her credit, she immediately recognizes it's rather passive-aggressive and decides not to send it): “Dear Kristy, I’m sorry you’re the biggest, bossiest know-it-all in the world, but what can I do about it? Have you considered seeking professional help?”
- Spell My Name with an "S": It's Mary Anne, not Mary Ann/Marianne/Mariann/Maryann/Maryanne/Mary-Ann/Mary-Anne/etc.
- Tender Tears: One of her defining traits.
- Tomboy and Girly Girl: Girly Girl to Kristy's Tomboy. She's utterly sensitive, romantic, cries easily, hates sports and loves sewing and knitting, has a fondness for kittens, and after her father stopped being so strict (book 4), she starts caring about her clothes, hairstyle and appearance, unlike Kristy who couldn't care less.
Stacey Mc Gill
Anastasia Elizabeth McGillKnown as Stacey. Originally from New York City, she moved to Stoneybrook when her father was transferred. Frequently described as chic, sophisticated and "boy-crazy", Stacey, like Claudia, had many boyfriends but few long-lasting relationships. She was the treasurer of the club, as she had a gift for mathematics. She moved back to New York in Goodbye, Stacey, Goodbye when her father was transferred back, but returned to Stoneybrook in Welcome Back, Stacey when her parents divorced, and her mother decided that she preferred living in the small-town environment. Frequent attention is paid to the fact that she is diabetic, and she is hospitalized multiple times throughout the series. She quits the club to spend more time with other friends in Stacey vs. the BSC, but she rejoins in Stacey and the Bad Girls.
- All of the Other Reindeer: In New York, after being diagnosed with diabetes (and therefore missing a lot of school and losing all her friends). It's the main reason why she and her family moved to Stoneybrook in the first place. Stacey does manage to repair her friendship with Laine Cummings, but even after she moves back to New York, she's never really accepted back into that social circle. One of the major reasons she decides to move back to Stoneybrook after her parents get divorced is that Laine is her only friend in New York, while in Stoneybrook she has the club.
- Big Applesauce: Stacey is constantly reminding the readers how awesome New York is. The other book narrators make a big deal out of Stacey being from the city as well.
- Big Sister Mentor: To Charlotte Johanssen, her favourite sitting charge. They're both only children who experience social isolation - Stacey because of her illness, Charlotte because of being ahead of her classmates.
- The Bus Came Back: After being Put on a Bus, she comes back to Stoneybrook with her mother in the book Welcome Back, Stacey!.
- Cool Big Sis: Again, to Charlotte. In later books they sometimes even call each other "Big Sis" and "Little Sis."
- Do Not Call Me Paul: Stacey does not like being called Anastasia.
- Embarrassing First Name: Stacey doesn't tell anyone her real name is Anastasia for a long time.
- Embarrassing Nickname: Her father calls her "Boontsie".
- Everyone Loves Blondes: Blonde, pretty, smart, fashionable and very popular at school. While she wasn't that popular when living in New York, she's seen as the "sophisticated New Yorker" in Stoneybrook.
- The Fashionista: It is stated repeatedly throughout the series (at least once a book) that Stacey is glamorous, trendy, and loves clothes and shopping.
- Friendless Background: In New York, the run up to Stacey's diagnosis with diabetes was full of instances of her getting sick, including fainting at school and wetting the bed at a sleepover. Stacey was constantly being dragged out of school for more doctor's visits and tests. Because none of her friends knew what was going on — just that she was somehow sick, possibly contagious, and missing enough school that she almost had to repeat sixth grade — they started ostracizing her after the bedwetting incident. One of the reasons her father accepted the transfer to Connecticut was to get Stacey away from the bad memories. See All of the Other Reindeer.
- Good with Numbers: She's the club treasurer on account of being a math whiz.
- Hormone-Addled Teenager: One of the books is even called "Boy-Crazy Stacey".
- Ill Girl: In general, but particularly in Stacey's Emergency.
- Only Known by Their Nickname: We don't even learn that Stacey is a nickname until Dawn takes her place as treasurer; Kristy wants to use their full names for a quick ceremony transferring the office.
- Overprotective Dad and Mom: After she is diagnosed with diabetes.
- Put on a Bus: When Stacey's father gets transferred back to New York.
- Saw "Star Wars" Twenty-Seven Times: In Kristy's Big Day, she confesses that she watches Mary Poppins once a week, totaling hundreds of times.
- Smitten Teenage Girl: Regularly crushes on other guys and has crushed on two older guys.
- Spell My Name with an "S": It's Stacey, not Stacy.
- When You Coming Home, Dad?: Stacey's dad is a workaholic.
Dawn Read SchaferIntroduced in Mary Anne Saves the Day, Dawn is the alternate officer of the club. Originally from California, Dawn moves to her mother's hometown of Stoneybrook when her parents divorce. She becomes fast friends with Mary Anne, which makes Kristy extremely jealous. She is identified throughout the series as being a very casual, individual health-food nut, though this was retooled in later books to place the emphasis more on environmental activism and strict vegetarianism, rather than simply being into health food. Her mother and Mary Anne's father marry in Mary Anne and the Great Romance. Later in the series, she grows increasingly homesick, and moves back to California to live with her dad and younger brother in Dawn's Big Move.
- Bratty Teenage Daughter:
- In Here Come the Bridesmaids! when her father is getting remarried. She all but pitches a fit because her stepmother-to-be doesn't want to have Mary Anne as a bridesmaid as well as Dawn. Remember, Mary Anne is Dawn's stepsister on her mother's side and is not remotely related to Dawn's father, let alone his new bride. However Dawn never asked if Mary Anne could be a bridesmaid. She just assumed that Mary Anne would be sharing the moment with her and bought her a dress. To Dawn's credit, she never brings up her (frankly, stupid) assumption to her father or stepmother. But Mary Anne still ends up wearing the bridesmaid dress, because she assumed it'd be a church wedding, not a beach wedding, and didn't pack appropriately. One has to wonder just what Dawn's father and stepmother thought about that.
- In Dawn and the We Love Kids Club. She was so upset by her father deciding to remarry that she stole his credit card and flew back to Connecticut alone. Considering her dad does break up with his fiancee shortly afterward (they do eventually get married, see above) and that Dawn practically threw her mother at her second spouse, yeah.
- Characterization Marches On:
- In early books, Dawn is into health food and "prefers" to not eat red meat, but still eats chicken and fish. In later books, she is a strict vegetarian.
- Her first book had her convince her just as health foodie Mom that they must serve things like hot dogs at their BBQ because this is what most residents of Stoneybrook eat. Later she makes a big deal out of things like cold cuts being served.
- In the very first book where she appears, according to Mary Anne (the narrator), Dawn is "not exactly pretty". In later books she is always described as drop-dead gorgeous.
- Books like Jessi Ramsey, Pet Sitter and Kristy and the Mother's Day Surprise also describe her as very organized — not as organized as Mary Anne, but significantly more so than the other club members, which is why she's a good treasurer in the absence of Stacey. She's written this way mostly as a contrast to her mother. However, after her mother marries Mary Anne's father, she loses this trait and becomes much more casual and unconcerned with any kind of neatness, so that she and her mother would contrast Mary Anne and Richard Spier.
- Clingy Jealous Girl: Shows a dose of this in Mary Anne's Makeover, in which she admits that she's jealous of all the time Mary Anne's been spending with her father and that it makes her miss her own terribly. Dawn comes off as being resentful of Mary Anne for having her father around, apparently forgetting that he is Mary Anne's only living parent.
- Cloudcuckoolander's Minder: For her mother.
- Cool Big Sis: Most of the time she gets along with her younger brother.
- Country Mouse: In Stacey's Mistake when the girls go to visit Stacey in New York.
- Embarrassing Middle Name: Read.
- Embarrassing Nickname: "Sunshine". Part of the reason it embarrasses her is because it's also her California best friend's full first name.
- Granola Girl: She loves the beach and California living, is a health food nut, an environmentalist, and a strong opponent of guns and violence.
- Hair of Gold, Heart of Gold: She's described as a really beautiful 13-year-old girl with very long blonde hair, so light it looks almost white. Dawn is also a very idealistic Granola Girl who cares about environment.
- Informed Attribute: Dawn is usually described as being the "individual" of the group, but at times she changes herself to attract boys. For instance, in Dawn and the Older Boy, she cuts her hair so a boy will like it better.
- It's All About Me: At her worst. Most notably in Dawn Saves The Planet and the above-mentioned example in Mary Anne's Makeover.
- New Transfer Student: She comes to Stoneybrook Middle School in the middle of the seventh grade and befriends Mary Anne.
- Put on a Bus: Eventually she moves back to California.
- Rapunzel Hair: She has long waist-length blonde hair
- Sixth Ranger: More like fifth ranger. She joins the club at the end of the book "Mary Anne Saves The Day", becoming the official fifth member.
- Soapbox Sadie: Infamously played straight in Dawn Saves The Planet. By the end of the story, it ends up blowing up in her face.
Mallory PikeFirst introduced in The Truth About Stacey as a ten-year-old client, she is invited to join the club at age eleven in Hello, Mallory!, after Stacey moves back to New York. The oldest of eight kids, Mallory is described as very responsible with children. Despite this, at first the club is hesitant to let her join because of her age, making her do a number of difficult tests before finally relenting and letting her and her best friend Jessi join the club. As she is the only one in her family with red hair, glasses and braces, Mallory often feels unattractive and an ongoing plot arc of hers was trying to convince her parents to let her spice up her look with contacts, pierced ears, and a new wardrobe. She is forced to leave the club for a while when she comes down with mononucleosis in Get Well Soon, Mallory. She rejoins the club in Kristy and the Copycat, but then leaves for good in The All-New Mallory Pike when she leaves for boarding school.
- All Girls Like Ponies: She's a bookworm who especially loves reading horse stories.
- Ascended Extra: She started out as a baby-sitting charge, because her family, the Pikes, are a frequent client of the Baby-sitters Club since the first book.
- Ascended Fanboy: She has always admired the girls and was excited when they asked her to join the club.
- Bookworm: Mallory is an avid reader, and she also like to write stories.
- Butt Monkey: A list of the tragedies that befall her can be found here.
- Cool Big Sis: She's very good with children, due to her experience with seven younger brothers and sisters.
- Friendless Background: She had no friends before meeting Jessi and joining the BSC.
- I Am Not Pretty: How Mallory sees herself.
- In-Series Nickname: She's often called "Mal".
- Massive Numbered Siblings: The Pikes have eight children, including identical triplets.
- Meaningful Name: This is most likely completely unintentional, but "Mallory" is Norman French for "unlucky" and fans of the series see her as the resident Butt Monkey and Memetic Loser.
- Meganekko: Mallory wears glasses.
- Most Writers Are Writers: She is an aspiring writer.
- Naïve Everygirl: The typical insecure teenage girl. She sees herself as ugly and feels like her parents treat her like a baby.
- Off to Boarding School: In The All-New Mallory Pike. In this case, however, going was her decision.
- Only Sane Woman: In many books where the club members are fighting, Mallory and Jessi serve as this. She's also usually the sanest one in her family.
- Redheads Are Uncool: As Mallory is the only one in her family with red hair, glasses and braces, she often feels unattractive and an ongoing plot arc of hers was trying to convince her parents to let her spice up her look with contacts, pierced ears, and a new wardrobe. She also feels like her parents treat her like a baby.
- Self-Deprecation: With her insecurities about her age (she's only eleven!), looks (she has braces and glasses), and often feeling frumpy and awkward.
- Sixth Ranger: She joins the club along with Jessi in the book "Hello, Mallory".
- Straw Fan: In Mallory Pike, #1 Fan, she comes across like this.
- Team Mom: She acts like this for her seven younger siblings, most notably in the book where their father loses his job; she helps them form 'the Pike Club' to deal with the situation on their own terms.
- Those Two Girls: With Jessi.
Jessica Davis "Jessi" RamseyJessi moved to Stoneybrook from Oakley, New Jersey at the beginning of the sixth grade, coincidentally into Stacey's old house. She has an eight-year-old sister called Rebecca or "Becca," and a baby brother named John Phillip Ramsey Jr., better known as "Squirt." Jessi is incredibly talented at ballet, and when she grows up she wants to become a professional ballet dancer. She has been doing ballet since she was four, and was admitted into a special ballet school in Stamford. She has had the lead role in several productions at that school. In book #115, Jessi's Big Break, she had an opportunity to join the Dance New York programme and study ballet under David Brailsford for 3 1/2 weeks. Toward the end of the story, she was also given a chance to join the Dance New York programme full time, but she decided to accept it when she was a little older.
- The Ace: All the BSC girls are this to some exent, but Jessi really stands out. She's a Cunning Linguist, a ridiculously talented ballet dancer who always gets the lead roles in productions at her ballet school (despite being the youngest in the class). After taking only a few synchronized swimming lessons, she obviously wins a gold medal at the end, despite her lack of experience.
- All Girls Like Ponies: Not as much as Mallory though.
- Black Best Friend: To Mallory and the other girls.
- Bookworm: When Jessi and Mallory become friends, they bond over their shared love for books, especially horse stories. Of course this was less emphasized in Jessi's later books, because while Mallory is an aspiring writer, Jessi's primary activity is ballet.
- Characterization Marches On: In Jessi's first appearance, ("Hello, Mallory") we learn that Jessi loves to tell jokes, and apparently "knows more jokes than anyone in the world”. This trait is pretty much forgotten in later books.
- Cool Big Sis: She's very close to her little sister and always takes care of her 14-month-old brother.
- Cunning Linguist: As we learn in Jessi's first book, she is "good at languages": fluent in Spanish after just a one-week holiday in Mexico, and immediately able to learn sign language in order to communicate with a deaf boy.
- Divergent Character Evolution: Essentially Mallory 2.0 before later books explored her character.
- Friendless Background: Of the Newcomer variety. Doesn't help that many people are racist towards her and her family.
- New Transfer Student: Jessi was born in Oakley, New Jersey. Jessi and her family moved to Stoneybrook when she was 11.
- Only Known by Their Nickname: No one calls her Jessica, expect her Aunt Cecelia and her ballet teacher, Mme Noelle.
- Only Sane Woman: Like Mallory, she doesn't go overboard on something like many of the other girls.
- She's Got Legs: Jessi has the very long legs a dancer needs, and often lampshaded. Mallory notices her legs the first time she meets Jessi.
- Sixth Ranger: She joins the club along with Mallory in the book "Hello, Mallory".
- Spell My Name with an "S": It's Jessi, not Jessie.
- Those Two Girls: With Mallory.
- Token Minority: As every single book will tell you, she is the only black member.
Abigail "Abby" StevensonThe final Sixth Ranger, taking over after Dawn left and Demoted to Extra as soon as Friends Forever started up. Abby moved with her mom and twin sister, Anna, from Long Island to Kristy's neighborhood in part for her mom to distance herself from Abby's father's death. Abby is a big joker, a natural athlete, asthmatic and allergic to half the things in any given room.
- Alter Kocker: Abby's Grandpa Morris and Gram Elsie in Abby and the Mystery Baby. Less so in other appearances.
- Blithe Spirit: Greatly enlivens BSC meetings with her jokes and her refusal to take Kristy too seriously.
- Disappeared Dad: Abby's father was killed by a drunk driver prior to her series debut.
- Genki Girl: Just as outgoing and enthusiastic as Kristy, but more easygoing.
- New Transfer Student: Abby moved to Stoneybrook with her mother and her sister when she was 13.
- Only Known by Their Nickname: Usually called just "Abby".
- Passionate Sports Girl: She's very athletic like Kristy and soccer is her favorite sport.
- Polar Opposite Twins: Abby and Anna.
- Pungeon Master: She's always making silly puns and corny jokes.
- Sixth Ranger: The last sitter to join the BSC, replacing Dawn.
- Technician vs. Performer: According to Kristy, Abby is a natural athlete, while Kristy is a sportsperson.
- Tomboy and Girly Girl: The tomboy compared to her twin sister Anna, who is quiet and loves to play the violin.
- When You Coming Home, Dad?: Abby's mother is like this. Possibly justified to an extent, since she's a single parent with two teenagers to support.
David Michael ThomasKristy's little brother and most frequent sitting charge, at least in the first book or two.
- Annoying Younger Sibling: Happens more as he grows older; in the first few books, he's still a pretty little guy and very sweet.
- Rags to Riches: Like Kristy, on account of their mother's remarriage to a millionaire.
- Two First Names: Three first names, actually.
- The Unfavorite: Gets this treatment from his father in Kristy's Big News, where he's the only one of the four Thomas kids not invited to the wedding - or even to participate in the phone conversation.
- Vitriolic Best Buds: With Karen.
Karen BrewerDaughter of Kristy's stepfather Watson from his first marriage. Neither of the girls has ever had a sister, which helps them to bond.
- Annoying Younger Sibling: Though Kristy gets along well with her.
- Author Avatar: The author describes her as the kind of child she'd love to have been.
- Bratty Half-Pint: She's quite bossy, talkative, and loves to scare people.
- Genki Girl: The opposite of her shy brother Andrew.
- Girls Love Stuffed Animals: She has two identical stuffed cats, Moosie and Goosie, one at each of her parents' houses.
- Middle Child Syndrome: She is the Jan Brady of her blended family, between straight-As, super-ambitious Kristy and adorable two-year-old Emily Michelle. Sometimes she has a hard time coping with it, especially because her Daddy, Watson, dotes on his stepdaughter Kristynote and adopted daughter Emily, who live with him full time, while his custody arrangements with Karen's mother means she only gets to see him every other weekend or, in later books, every other month.
- Ms. Imagination: Her wild and active imagination (especially with scary stories) is probably her defining trait, and sometimes it can get out of hand.
- Nightmare Fetishist: She loves to tell stories about ghosts and witches, and has most of the babysitters convinced.
- Sibling Yin-Yang: With Andrew.
- Wise Beyond Their Years: So bright that she has already skipped a grade in school.
Andrew BrewerKaren's little brother.
- The Quiet One: In contrast to his sister, he doesn't talk too much.
- Shrinking Violet: Usually very shy.
- Sibling Yin-Yang: With Karen.
Charlotte JohanssenOne of the sitting charges. She's an extremely bright child. She and Stacey become very close and regard each other as honorary sisters.
- Brainy Brunette: She has brown hair, and is a very smart student.
- Canine Companion: Her schnauzer, Carrot.
- Intelligence Equals Isolation: In the third book it's revealed that she's bullied by her classmates for being so smart. She gets to skip a grade, which resolves the issue.
- Loner-Turned-Friend: After Stacey helps her out of her shell, she becomes a little more extroverted and finds a lot of friends (like Becca, Jessi's sister).
- Shrinking Violet: She's very shy, especially in her early days.
- Wise Beyond Their Years: Charlotte initially has trouble getting along with her classmates because she was much smarter than them.
Jamie NewtonA longtime sitting client, who regards Kristy and Claudia as his favorite sitters. He stays with Kristy when his mother gives birth to his baby sister Lucy.
- Adorably Precocious Child: Sometimes, he tries to act mature, but still has a childlike and playful personality that makes him very cute.
- Big Brother Instinct: Towards Lucy.
- Cheerful Child: A very friendly 5 year-old kid, and rarely in a bad mood.
- The Cutie: Usually very sweet and affectionate. All the sitters find him adorable.
Myriah PerkinsThe eldest daughter of the family who moves into Kristy's childhood home after Kristy's mom remarries and the Thomases move to Watson's mansion.
- The Ace: A multi-talented little girl, Myriah loves singing, dancing, and swimming. She also knows gymnastics.
- Adorably Precocious Child: The reason why she and Gabbie are unanimously adored by all the sitters.
- Cheerful Child: She's usually upbeat, outgoing, and adorable.
- Genki Girl: But not in an annoying way.
- Wise Beyond Their Years: She's very bright and acts much more mature than her age.
Gabbie PerkinsMyriah's younger sister.
- Adorably Precocious Child: As smart and precocious as she is, Gabbie is still a cute and huggable 2 and-a-half-year-old little girl.
- Cheerful Child: Like her sister, she has a very happy and friendly attitude.
- The Cutie: Very much so, she often says cute things like "toshe me up" ("pick me up & give me a hug").
- Full-Name Basis: She always calls people by their full names.
- Wise Beyond Their Years: She's two years old, and yet speaks in complex full sentences and acts more like she's around TEN!
Adam, Byron and Jordan PikeMallory's younger brothers, identical triplets.
- Annoying Younger Sibling: They are noisy, mischievous, and sometimes Mallory is annoyed by their antics.
- Big Brother Bully: All three to Nicky. Especially in "The Ghost at Dawn's House".
- Big Eater: All of them, but Byron especially
- Same-Sex Triplets: Identical triplet brothers.
- Trickster Twins: Trickster Triplets, actually.
Vanessa PikeThe second-oldest Pike girl.
- Annoying Younger Sibling: Vanessa speaks in rhyme often, which drives everyone crazy.
- Cloudcuckoolander: Her rhymes and obsession with poetry make her this.
- Ms. Imagination: Very creative and often lost in her own world.
- Rhymes on a Dime: She wants to be a poet.
Nicky PikeThe youngest of the four Pike boys, and the only one who isn't a triplet.
- Butt Monkey: Especially when the triplets are around.
- Middle Child Syndrome: He has a particularly isolating case. The eight Pike kids are four girls (Mallory, Vanessa, Margo, and Clair) and four boys (Nicky and the triplets). So Nicky is the odd man out, especially since in the early books he shares a room with the triplets. His three brothers don't want anything to do with him, Claire and Margo are inseparable and consider themselves best friends, and Mallory and Vanessa are older and spend more time with their friends.
Margo PikeThe second-youngest Pike, best known for her easily-upset stomach.
- Big Sister Instinct: Can be pretty protective of Claire, whom she sees as her best friend.
- Ill Girl: She gets sick easily. Pretty much her main trait.
Claire PikeThe youngest of the eight Pike children.
- Annoying Younger Sibling: In her worst days, she can be one of the most annoying of Mallory's siblings.
- Bratty Half-Pint: She is prone to throwing tantrums.
- Cloudcuckoolander: She goes through an extremely silly phase, calling everyone "Silly-Billy-Goo-Goo" and running around the house naked.
- Genki Girl: Sometimes.
- The Nicknamer: In some of the books where she does this, dubbing her parents "Moozie and Daggles" and tacking "silly-billy-goo-goo" onto other people's names.
Jeff SchaferDawn's 9/10-year-old brother. Best friends with the Pike triplets, Jeff is usually a comedian with a deep love of stupid jokes, but he does have a serious side. Having originally moved out to Stoneybrook with his mom and sister, his increasing homesickness for California and his father (and resultant acting out) led to his parents agreeing to split custody so that he could move back in with him.
- Annoying Younger Sibling: With some nuance. He annoys Dawn, but they're still very close and rely on each other quite a bit. He's absolutely thrilled when Dawn follows him in moving back to California.
- Deadpan Snarker: As much as the BSC ever gets, he has to answer everything with a joke.
- Hidden Depths: He is an incurable joker and he gets 10x more immature when with the Pike triplets, but when the situation gets serious, he's actually really good at wrangling younger children and can be incredibly resourceful and responsible. He stops the DeWitt boys from making a mess in the men's bathroom when Kristy sends him in to check on them, and in Baby-Sitters' Island Adventure, he spends a lot of time distracting the younger kids like Jamie and even manages to catch fish for them to eat.
- Outnumbered Sibling: He starts out with one older sister, Dawn, but by the end of the series, each parent's remarriage nets him a sister: his mom's stepdaughter, Mary Anne, and his dad's daughter with his second wife, Gracie.
Logan BrunoMary Anne's boyfriend and an associate club officer (basically a member who doesn't have to go to meetings). He moves into town from Louisville, Kentucky and is immediately smitten with the shy yet intelligent Mary Anne.
- A Day in the Limelight: Logan's Story and Logan Bruno: Boy Baby-Sitter, two books where Logan narrates the story himself.
- Big Brother Mentor: To the club members sometimes.
- Big Man on Campus: Implied many times to be popular at school.
- Celebrity Resemblance: Mary Anne initially liked him because he looks like her favorite actor.
- Control Freak: Not a trait that is always present, but it's the reason why he and Mary Anne break up for a while.
- Cool Big Bro: His style of dealing with kids, stemming from having two younger siblings of his own.
- Hormone-Addled Teenager: Logan assumes you (the reader) assume he's this. When he does the typical chapter two description of the club members in his two books, he, just like the girls, describes Claudia and Stacey as beautiful and fashionable — then he stops, and explains that just because he finds girls other than Mary Anne attractive doesn't mean that he's going to cheat on her or that he likes them better than Mary Anne, that Mary Anne is his girlfriend and that she's amazing, etc.
- Lovable Jock: He's on the Stoneybrook Middle School football, baseball, volleyball, and track teams, and also a very nice guy.
- Nice Guy: How he's usually portrayed, except in "Mary Anne Vs. Logan" where he acts like a controlling jerk.
- Off to Boarding School: He was almost sent away to his dad's old boarding school but he and Mary Anne managed to talk his father out of it.
- The One Guy: The only male member of the BSC.
- Real Men Wear Pink: Enjoys baby-sitting, despite the stereotype that it's a "girly" activity.
- Sixth Ranger: Somewhat. He never becomes a fulltime member of the club, just an associate.
Shannon KilbourneThe second associate club officer, Shannon was invited to join the club on a more permanent basis but declined as she was too busy with her other extra-curricular activities to commit to the club meetings. Shannon was introduced when Kristy moved across town to live with her new rich step-father, and was originally portrayed as a "snobby" foil to Kristy. Shannon became a full member of the club briefly in books 67 - 81, when she replaced Dawn as the alternate officer.
- The Ace
- Ascended Extra: Unlike Logan, who is both Mary Anne's boyfriend and the other girls' classmate and thus often present during school plotlines or crowd scenes, Shannon is just a neighbor of Kristy's, and later, Abby's. She's usually just a footnote in the explanation of an Associate Member of the club is, but there was a brief stretch of books (including Mysteries and at least one Super Special) where she replaced Dawn as the Alternate Officer and was a regular at club meetings and babysitting B-plots. She also makes a random guest appearance in Dawn's Family Feud, while Dawn and Mary Anne are on vacation, to help Claudia sit for the Barrett-DeWitts.
- A Day in the Limelight: Shannon's Story
- Embarrassing Nickname: Shannie. She doesn't mind her charges calling her that in her initial appearance, but it embarrasses her when her mom uses it.
- Everyone Loves Blondes: Lampshaded in the book where Kristy reminisces about how she first met Shannon (whom she intensely disliked at first) and snarks about the trope in relation to Shannon and her friends, who are all blonde.
- Extracurricular Enthusiast: An overachiever who attends a private school, involved in many extracurricular activities.
- Jerk with a Heart of Gold: Ends up bonding with Kristy when Kristy's dog passes away, despite having been engaged in a vicious prank war with her before that.
- Lovable Alpha Bitch: Being a Rich Bitch was her original characterization in "Kristy and the Snobs" but gets better after Character Development, and she and Kristy eventually become friends.
- One Steve Limit: Averted; Kristy's brother names their new dog Shannon after the human Shannon. Most books featuring both point out this confusion.
- Rich Bitch: She started out as this, although it was less because she genuinely looked down on Kristy and more because she didn't want Kristy and her friends to take away her baby-sitting jobs.
- Silk Hiding Steel: When Kristy and the BSC first babysit for the Delaneys, the children boss them around and treat them like servants. Kristy ends up going along with it, getting them drinks and so on. When they try this on Shannon, who has been babysitting them for years, she just lifts an eyebrow and they meekly get their own drinks.
- Sixth Ranger: But like Logan, she never becomes a fulltime member of the club.
- We Named the Monkey Jack: Shannon gives a puppy as a gift to the Brewer/Thomas family, that was also named Shannon after her.
Charlie ThomasKristy's oldest brother. When the Thomases move to Watson's neighborhood, the club starts paying Charlie to drive Kristy to and from club meetings so she doesn't have to give it up, since it's too far to walk.
- Team Dad: To his younger brothers and sister. It's revealed in Kristy's Big News that after their father walked out on the family, he quit his school's baseball team in order to take care of them in the afternoons while their mother worked.
Sam ThomasKristy's middle brother. He has a mutual attraction going on with Stacey and likes to prank-call the club during meetings.
- Ship Tease: With Stacey.
Janine KishiClaudia's older sister, a certified genius high school student who takes classes at the local community college.
- Big Sister Instinct: YOU NEVER ACCUSE AND/OR FRAME CLAUDIA FOR CHEATING ON A TEST AND EXPECT TO GET AWAY WITH IT.
- Brainy Brunette
- Character Development: She starts to come out of her shell a little more as the series goes on. Claudia even notes that after Mimi's death she spends less time at her computer.
- Cool Big Sis: She has her moments and reveals to Claudia that she has a hidden candy stash in her room.
- The Glorious War of Sisterly Rivalry: With Claudia. She the "smart one".
- Foolish Sibling, Responsible Sibling: The Responsible to Claudia's Foolish.
- Sibling Yin-Yang: With Claudia.
Cokie MasonA classmate of the girls who resents them and tries frequently to make them look ridiculous.
- Hoist by His Own Petard: Every time she tries to prank the club.
- Only Known by Their Nickname: Her real name is Marguerite.
- The Rival: To the club, but especially Mary Anne.
Grace BlumeCokie's best friend.
- Lovable Alpha Bitch: Actually becomes friendly with the girls on occasion.
Alan GrayOne of the girls' classmates, a practical joker who nurses a crush on Kristy.
- Jerk with a Heart of Gold: In elementary school, he teases Mary Anne about bringing her father to the Mothers' Day event. After Kristy tells him off and explains that Mary Anne's mother died, he promptly apologizes, saying he'd never have made fun of her if he knew.
- Loving Bully: To Kristy.
- Vitriolic Best Buds: Kristy may find him annoying, yet she acknowledges he's fun and even invites him to Mary Anne's surprise party.