Peg - The main character, together with Cat. She is a young girl who wears a redhat and blue dress. She explains the situation in each episode directly to the "camera", announces when they have "a big problem", and reasons out solutions to math-related problems. During songs, she pulls out a ukulele and plays it. She has a special blue marble hidden under her hat. Her favorite crayon is "little bluey". She is voiced by Hayley Faith Negrin.
Cat - An indigocat whose best friend is Peg. He loves circles and accompanies Peg on her adventures. Cat often inspires Peg to realize a solution to a problem without being aware of it himself. Often helps to calm Peg when She "totally freaks out". He was inspired by Jennifer Oxley's pet cat. He is voiced by Dwayne Hill.
Ramone - A boy who shows up to help Peg and Cat with their math problems. He is voiced by Thamela Mpumlwana.
Pig - A pig who is usually silent except when he sings in a rich operatic tenor. His favorite shape is the triangle. Voiced by Tommy Wazelle.
Neighbor Ladies- A female African American character named Viv and a female Asian American character named Connie that appear in several episodes. They often accidentally add to Peg and Cat's problems by trying to be nice.
100 Chickens - Chickens who play and live on farm and travel to space with Pig, Peg, and Cat. Voiced by Rob Morrison and Carys Casucci.
The Pirates and their parrot - A quarrelsome quartet of pirates who live on an island. They like to sing in four-part harmony but sing "really bad" when they get cranky. They have had a sleepover with Peg and Cat. Voiced by Rob Morrison.
Big Mouth - A blue, furry, horned space monster who likes to eat things that are little and yellow.
Richard - A space alien from the purple planet who plays with Peg and Cat in space. He often cries during tense situations. Voiced by Christian DiStefano.
The Teens - Three cool older kids who love pizza and texting on their phones, but can't stand getting dirt on their clothes. Tessa is thirteen, Mora (voiced by Annick Obonsawin) is fourteen, and Jesse is fifteen.
Giants - Peg and Cat's big friends who live up the beanstalk in Fairy Tale Land. In The Giant Problem Peg and Cat think that the Giants are going to eat them. Voiced by Bryce Kulak (Giant) and Shoshana Sperling (Giantess).
Mermaid - A swimming damsel who lives in the Magical Forest. The Pig stole her Golden Pyramid's in The Golden Pyramid Problem. She is voiced by Emilie-Claire Barlow.
The Three Bears, The Three Pigs, The Three Billy Goats Gruff - Nine Friends of Peg and Cat that get into bands like The Electric Eleven. Voiced by Kevin Brathwite (Papa Bear), Angela Teek, (Mama Bear), Phatt Al (Baby Bear), and Rob Morrrison (Three Little Pigs and Three Billy Goats Gruff).
The Blockettes - Five Dancers that dance in the Radio City Music Hall.
Mac - A gruff-voiced man who works various jobs in different episodes.