Janice never appeared in the comic strip. She was introduced in the TV special, Why, Charlie Brown, Why? In that special, Janice is a new student at Charlie Brown and Linus' school, and has also befriended them. She likes to play on the school swings. However, after she becomes ill at school one day, she's diagnosed with leukemia, and has to go to the hospital. She loses her hair as a result of the treatment she receives, and has to challenge the teasing of a schoolyard bully (who is told off by Linus), as well as the resentment of her sisters due to the attention she receives. At the end of the special, she has apparently recovered, and her hair grows back. She has a notably optimistic and brave attitude toward her illness, hoping to eventually recover and return to her normal life, as she says when she's at the hospital: But I'm going to get well, and go back to school and swing on those swings!.
Janice has some similarities with the other minor Peanuts character Lila. The two girls look similar and both characters are hospitalized due to illness at one point, although in Janice's case her illness was clearly specified.
Janice was voiced by Olivia Burnette.