6 until Karen's Birthday
Karen is described as having long blonde hair, blue eyes, freckles and wears glasses (she has blue glasses for reading & pink glasses for everything else). She is frequently seen in her pink shirt with a unicorn on it.
Karen is the stepsister of Kristy Thomas, who is one of Karen's favorite people.
Karen was born on a spring Saturday afternoon at 2:35 p.m. Watson picked her name which means "pure" because he felt pure joy in seeing his daughter.
Karen describes herself and her brother Andrew Brewer as "two-twos" (that she got from a book called "Jacob Two-Two Meets the Hooded Fang") because they split their time between the "little house" (which is their mom's house) and the "big house" (which is their dad's house).
Karen and Andrew tend to have two of most things since they spend a lot of time at each of their parents' houses.
In the book "Little Miss Stoneybrook...and Dawn", Kristy helps Karen enter the Little Miss Stoneybrook pageant. The pageant is for girls ages 5 to 8. In the pageant Karen wears the dress that she wore in her father and stepmother's wedding. For her talent, she sings "The Wheels on the Bus", but she added so many extra, made up verses to the song that the judges began looking at their watches because she took too much time. For the interview part, Karen was asked "If your house was on fire and you could only rescue three things, what would they be, and why?" Karen had practiced the questions with Kristy and knew what she was supposed to say (nice answers like saying she would rescue her family), but instead she said she would rescue her toys and her blanket. Karen did not win anything in the beauty pageant and she was sad and cried.
When she began kindergarten, she was put in the first grade during Christmas. After spending a week in first grade, Karen's teachers decided to move her to the second grade.
In the graphic novels
Karen appears in the graphic novel versions of Kristy's Great Idea, Kristy's Big Day, and Claudia and Mean Janine. In the books she doesn’t appear in, (minus Dawn and the Impossible Three) Kristy would receive a call from Watson to sit for her and Andrew.
- Karen's two best friends are Hannie Papadakis and Nancy Dawes. The three of them call themselves the "Three Musketeers“, after they had a really big fight. Hannie’s big brother, Linny, teases them about it.
- Karen met Hannie on her first day of preschool and she met Nancy after her parents' divorce & she moved into the "little house" with her mother & brother.
- She used to be friends with Amanda Delaney until the Delaney family moved away to another neighborhood. Hannie does not like Amanda.
- After the Kormans moved into the Delaney's old house, Karen becomes close friends with Melody Korman. She is also friends with Shannon Kilbourne's younger sister Maria Kilbourne and Mallory Pike's sister Margo Pike.
- Karen has a pretend husband named Ricky Torres who sits next to her in class because he also wears glasses.
- She is also friends with classmates Natalie Springer and Bobby Gianelli (who used to be a bully).
- Karen has a pen pal named Maxie Medvin who lives in New York City. She is also pen pals with Ms. Coleman's niece Caroline who lives in Oregon.
- In Karen's Swim Meet she makes friends with a visiting girl named Kristin.
- In Karen's Big City Mystery she becomes friends with Matt Dilley.
- Jenny Webb on a vacation in Karen's Cowboy.
- Keegan from Shadow Lake in Karen's Ski Trip and Karen's Fishing Trip.
- Sandy in Karen's Island Adventure
Karen has pets who live in the "big house" and the "little house."
- In the "little house," her stepfather Seth Engle has a cat named Rocky and a dog named Midgie.
- Karen has a rat named Emily Junior who travels with her between her two houses.
- Karen found a cat named Growly in her shed & adopted it.
- In the "big house," her dad had a cat named Boo-Boo who later passed away and the family got a kitten named Pumpkin.
- Her stepbrother David Michael Thomas has a Bernese mountain dog puppy named Shannon.
- She and Andrew have goldfishes named Crystal Light the Second and Goldfishie that live in a tank in the playroom at Watson's house.
- Karen used to have a goldfish named Crystal Light, but it passed away while she was at her mom's house.
- Watson adopted a pony named Blueberry for Karen after visiting an estate sale.
- Karen has two stuffed cats named Moosie and Goosie (who look exactly the same). Goosie stays at the "little house" and Moosie stays at the "big house."
- After her stepfather Seth Engle accepted a job in Chicago, Goosie moved with Karen to her dad's house.
- She has a blanket named Tickly that she ripped in half to keep one piece at her mother's and father's house.
- Kristy Thomas
- Mr. Ed TV show
- Cherry Italian ice
- Being the leader
- Ms. Colman
- The Wizard of Oz movie
- Lemon Drop (music group)
- Being grounded
- being punished
- house rules
- her favorite jeans being missing (left at Mommy's house)
- having a mullet
- her favorite TV show Mr. Ed not being on
- having the chicken pox
- being bored
- getting into fights
- Karen takes her spelling seriously and is protective of her little brother.
- She believes her neighbor Mrs. Porter (or Morbidda Destiny) is a witch.
- She thinks that the attic in the Brewers' house is haunted by the ghost of Ben Brewer.
- Karen has to wear earplugs when she goes swimming. She likes to help out in the kitchen.
- She loves to make up games. She likes to play Let's All Come In and her favorite character in the game is Mrs. Mysterious (who dresses in black). Karen's favorite game is Going Camping.
- Karen attended Camp Mohawk one summer and even attended a circus camp with her friends.
- Karen can sometimes be bossy and loves to be the leader.
- Karen has been the hospital twice: when she broke her wrist while roller-skating and when she got her spleen removed after falling from her tree house.
- She also had the chicken pox at the same time as Emily Michelle during Halloween.
- Karen's "best enemies" are Pamela Harding & her friends Jannie Gilbert and Leslie Morris.
- As revealed in the graphic novel version of Claudia and Mean Janine, Karen seems to have a hatred for Jenny Prezzioso.
- Her pediatrician is Dr. Dellenkamp.
- In Karen's Twin she mentioned that she wanted to have a job and kids when she is older.
- She likes to hang out by the stream in Mary Anne and the Playground Fight.
- She plays on a basketball team in Claudia and the Little Liar.