Samantha "Sam" Albertson
Portrayed in youth by Gaby Hoffman and in adulthood by Demi Moore.
- Aloof Dark-Haired Girl: Sam is brunette and becomes this as an adult, more independent and out of touch with her former best friends.
- Brainy Brunette: Sam is the nerdy one, full of ideas and interested in the supernatural.
- Bookworm: Sam loves to read science-fiction and is shown secrely reading an Edgar Allen Poe book when she's supposed to be asleep.
- Character Development: Learns as a cynical adult what Crazy Pete said was true; you can't let the bad things in life stop you from enjoying the good.
- Deadpan Snarker: The snarkiest of all the girls.
- Determinator: Sam is fixated on solving the mystery around Dear Johnny's death.
- Four-Philosophy Ensemble: The cynic. Changes her worldview in the end, though.
- Tomboy and Girly Girl: Tomboy to best friend Teeny's Girly Girl. Sam has no girly interests at all and gets in a fight with a boy, while Teeny is more interested in flirting with guys and loves fashion.
Portrayed in youth by Christina Ricci and in adulthood by Rosie O'Donnell.
- D-Cup Distress: Is seen bounding her developing breasts while dressing, though she gets rid of the bandages later.
- Four-Philosophy Ensemble: The apathetic initially, then the conflicted when she finds the truth about her mother's death.
- Girliness Upgrade: Is seen in a much more feminine outfit in the last scene of the girls as kids, after her first kiss with Scott, though still in pants.
- The Lad-ette: Roberta is a sporty tomboy Raised by Dudes. She dislikes all the answers in Teeny's Cosmo dating quiz and Chrissy, exasperated, asks her why she can't just "act like a girl".
- Lovable Jock: Roberta loves sports and gets along pretty well with everyone but the Wormers.
- Raised by Dudes: Why she's so tomboyish.
- Tomboy and Girly Girl: Tomboy to Chrissy's Girly Girl. Roberta is a jock, doesn't mind getting dirty, and fights with boys. Chrissy hates sports, is very neat, and reminds Roberta to "be a lady".
Tina "Teeny" Tercell
- The Fashionista: Loves dressing up in fancy clothes.
- True Blue Femininity: Wears a lot of blue, much more than the other girls.
Christina "Chrissy" De Witt later Williams
Portrayed in youth by Ashleigh Aston Moore and in adulthood by Rita Wilson.
- Beware the Nice Ones: Do not fake your death around Chrissy!
- Etiquette Nazi: Somewhat. Gets on the girls' cases for swearing, especially in the original script.
- Fat Best Friend: Though more chubby than outright fat. However, as an adult she's the skinniest and Roberta is the biggest, ironically.
- Fiery Redhead: Averted as auburn-haired Chrissy is the calmest and most proper of the group.
- Happily Married: ...to the nerdy kid she detested as a kid, no less.
- Naive Every Girl: Has shades of this.
- Only Sane Woman: She's the only one with common sense who tries to reign in the others when their adventures get a little too risky.
- Pink Means Feminine: And how! Chrissy's entire room is decorated in pink and her outfits, even into adulthood, always have it on them. Even her bike is pink.
- The Reliable One: Chrissy is the one who keeps count and hold of the treehouse money, keeps the group together, and reunites them as adults after they've gone their separate ways.
- All Love Is Unrequited: But he somehow does end up getting the girl.
- Character Tic: Has a habit of pushing his Nerd Glasses back.
- Extraverted Nerd: Doesn't let Chrissy's total disinterest stop him.
- Verbal Tic: "Hello, dear." "Yes, dear."