[5] Charles M. Schulz modeled Peppermint Patty after a favorite cousin, Patricia Swanson, who served as a regular inspiration for Peanuts.

[6] Schulz had also named his earlier character Patty after Swanson,[6] and he coined his well-known phrase "Happiness is a Warm Puppy" during a conversation with her in 1959.

[8] In later years, especially after lesbian groups began identifying with Peppermint Patty, Schulz downplayed the fact that the character was based on Swanson to protect her privacy.

Jazz pianist Vince Guaraldi composed the eponymous theme song for Peppermint Patty in 1967, making its first appearance in the television special You're in Love, Charlie Brown.

[14] Peppermint Patty has chin-length hair that she describes as "mousy-blah",[15] most often depicted as a medium brown (though the color has sometimes appeared as orange-red or auburn, as in The Peanuts Movie), and has freckles.

She wears a green, striped collared shirt, black or dark blue shorts (long pants in The Peanuts Movie) with two vertical white stripes on each side, and she almost always wears sandals (brown in the comic strip and merchandise; green in animated appearances except in The Peanuts Movie) with her toes showing.

Peppermint Patty is noted for her persistent habit of profoundly misunderstanding basic concepts and ideas that most people would consider obvious, then blindly ignoring any counsel against her latest fixation which leads to ultimately embarrassing situations for which she blames those who warned her.

In a later phone call to Charlie Brown, Patty finally accepts the truth: "Let's just say my pride had the flu, okay, Chuck?"

She is widely known for receiving a D− grade on every school assignment or exam (in 1999, the final full year of Peanuts, her teacher presents her with a certificate naming her to the "D-Minus Hall of Fame").

The first time, Snoopy is unable to abandon her waterbed in the guest room to catch the burglars who are stealing from the house, and the second time, a girl poodle distracts him and becomes his fiancée (the engagement is called off on the day of the wedding), leading Patty to angrily call Charlie Brown late at night and order him to come to her house to replace Snoopy as watchdog.

Besides guard duties, Peppermint Patty also retains Snoopy's services in other ways, including as an attorney and as a figure skating coach.

Her full name, Patricia Reichardt, is first mentioned in the January 15, 1972, strip when she, with Snoopy acting as her attorney, openly challenges the school's new dress code that forbids shorts and sandals.

Patty is the most "tomboyish" girl in the comic strip; she is a star athlete, especially in baseball where her team regularly trounces Charlie Brown's.

[18] Marcie also called her "Priscilla" in A Charlie Brown Thanksgiving; however, this is a continuation of a reference Linus had just made to Longfellow's poem The Courtship of Miles Standish in which Standish asks John Alden to speak to Priscilla Mullins on his behalf (just as Peppermint Patty has asked Marcie to speak to Charlie Brown).

Patty frequently denied having a crush on Charlie Brown at first, writing him off as too wishy-washy and because she "could strike him out on three straight pitches", and during a game of Ha-Ha Herman crudely insulting him when she thought he was not listening.

Even this strip ended in a denial of sorts; Patty brought Marcie up to the front desk of the hospital and tried to have her admitted as a patient, saying, "I think she's sicker than he is!

Also, in the movie Bon Voyage, Charlie Brown, both she and Marcie were shown as being attracted to Pierre, the son of their host family in Paris.