So who is this adorable young chipmunk girl? From the name you should be able to guess ...
She's Jonah J. Chipmunk's little kid sister. Her name is Penelope Marmotini Chipmunk, and she is the biological daughter of Grace Adler & Martin Graham. She is probably about 5 or 6 years old at the beginning of the story (the present time where Jonah is bemoaning his plight) and in kindergarten. Jonah calls her "Penny".
Whereas Jonah is a very unconventional teenage boy, Penelope is the opposite. She is a very conventional little girl. She wears a pink overall dress (shown in picture), she has pigtails complete with bows and hair ties. She wears a heart necklace. She has that gentle sweetness of a girl. She gets along with other girls, and boys often like her or pretend to dislike her (as boys do at that age). Jonah and Penny don't quite get along. Penny teases Jonah for being so strange, and she makes fun of his relationship with Jonathan J. Jackrabbit, often teasing Jonah calling Jonathan his "boyfriend" (which Jonah finds incredibly annoying). Penny's father, Martin, dotes on her, and sides with her in any dispute between her and Jonah, causing further resentment and rivalry. She is kind of spoiled, and very much a daddy's little girl sort. She is the "good kid" of the family. She gets good grades and she seems to be the textbook definition of "normal". Jonah on the other hand has social and behavioral difficulties and doesn't always fully apply himself in school. As such Jonah often finds himself jealous of his "perfect little sister". Grace doesn't necessarily improve this family dynamic. She often sides with Jonah and excuses a lot of his issues because he's "special". Both Martin and Penny don't like this and think Jonah should be held more responsible. Jonah is regarded as childish and immature for his age, while Penny is regarded as precocious and "mature" for her age. She loves to talk about her day at school, her friends, and the various boys that she likes or that flirt with her. All this talk tends to bother Jonah since it sounds like Penny has this great social life, whereas for Jonah, aside from Jonathan, he finds it difficult to make other friends outside J&Js special little circle (also even those boys, aside from Jonathan, eye him with some suspicion).
We probably won't see too much of Penny, she doesn't play a large role in the story, but I thought it was a cute idea for Jonah to actually have a sibling, a girl sibling, to tease him about his feelings for Jonathan. It makes the family dynamic more interesting and makes sense in-universe (why wouldn't the marmotini's have another kid after all this time? Jonah is about 14 at the beginning of the story).
This character is from the storyline "Better Than Best Friends" commonly abbreviated BTBF.
