She looks much like her boyfriend, Porky Pig, except that she wears a dress and has braided black hair (which she originally did not have).
Petunia was introduced by animator Frank Tashlin in the 1937 short Porky's Romance. The film is a parody of a 1932 Walt Disney cartoon called "Mickey's Nightmare". Whereas Mickey Mouse marries his longtime girlfriend Minnie in that film, Porky's overtures toward Petunia bring him only the scornful laughter of his porcine paramour. Tashlin quickly adopted Petunia as a regular member of Porky's entourage and featured her in two more cartoons: "The Case of the Stuttering Pig" and "Porky's Double Trouble", both in 1937. Voice actors Bernice Hansen, June Foray, Mary Kay Bergman, and Grey DeLisle each performed Petunia's voice in various shorts. In addition, she appeared in the 1972 special Daffy Duck and Porky Pig Meet the Groovie Goolies, voiced by Jane Webb.
Petunia was a mainstay in various Looney Tunes Comics. She is also seen as a meet-and-greet character at the Six Flags theme parks with Porky.