Peggy Jean has long shoulder-length hair that comes down a bit at the forehead. In her hair, a hairbow sits. She wears a shirt with long sleeves and trousers with stripes.
In Snoopy's Town Tale, Peggy Jean's hair is fittingly brown, and she wears a green bow in it. She wears the same outfit as Heather, except her dress and socks match her hairbow, and collar and bow on her dress are a very pale green.
Charlie Brown first meets Peggy Jean at summer camp in the strip from July 23, 1990, and falls for her right away, although he does not speak to her until two days later. She continued to appear intermittently in the strip until mid-1999, a few months before it ended. As a result of his extreme nervousness upon meeting her, Charlie Brown mistakenly gives his name as "Brownie Charles," which she continues to use thereafter. Although eventually, it seems that he likes it when she calls him that.
Peggy Jean and Charlie Brown's relationship hits a brief snag almost immediately after it begins, however. At summer camp, Peggy Jean decides to hold a football down for Charlie Brown, who declines, for he worries that she will pull it away like Lucy does. Charlie Brown takes a long time to decide what to do, leading Peggy Jean to think that he does not trust her, causing her to go home upset. Peggy Jean comes back, the two make up and she kisses Charlie Brown in the process. An excited Charlie Brown goes so far as to call Linus on the phone to tell him about the kiss. Unfortunately, the phone is answered by Lucy who asks "What is this, an obscene phone call??!!"
Before they go home, Peggy Jean promises she will write to Charlie Brown everyday. The boy becomes very discouraged later that summer when he has not received one letter from her. Charlie Brown eventually finds out, that Peggy Jean had been writing to him, but addressed the letters to "Brownie Charles". Sally had kept sending away the mailman, telling him there was no one in the house named Brownie Charles.
Later, Charlie Brown wants to buy Peggy Jean some gloves for Christmas but does not have the money to buy them for her (Linus suggests he send her a card advising her to keep her hands in her pockets). Charlie Brown sells his entire comic collection in order to buy the gloves, only to meet Peggy Jean in the shop and learn that her mother had just bought her the same sort of gloves; in the end, Charlie Brown gives the gloves he bought to Snoopy so they do not "go to waste". This storyline was adaptated as a portion of the animated special It's Christmastime Again, Charlie Brown. Curiously, Peggy Jean is depicted in the special as a redhead, which may have led to viewers confusing her with the Little Red-Haired Girl (the original VHS release of the special even mistakenly referred to her as the latter character).
Charlie Brown likes Peggy Jean as much as the Little Red-Haired Girl, if not more, he even considers telling Peggy Jean about her and has a moral debate on what he should do. But on March 11, 1991, he discovers that Peggy Jean has moved away leaving him with no indication of where she lives. Apart from a brief mention six months later, Peggy Jean is never brought up again until her final appearance in the strip on July 11, 1999, she reveals to him that she has another boyfriend who is waiting at the soccer field, leaving Charlie Brown heartbroken.
Peggy Jean reappears in Snoopy's Town Tale, though oddly with her appearance retconned. She now wears a green dress that has a short skirt area. Peggy Jean's artwork pose for this game nearly matches Frieda's artwork pose for The Peanuts Movie.