Penelope is a bratty and harsh girl who sometimes acts immature to most people around her except for her friends and Cody. She seems to dislike most boys as revealed in "Junior's Sleepover Mission!". She doesn't like it when people stereotype girls for only talking about boys and doing their nails and getting pimples. She also gets upset easily. In "Jeffy's 18th Birthday!", Brooklyn Guy told Rose that she would eat crackers, and the crumbs would get stuck between the seats, which is why she wasn't allowed to ride in his Hyundai Sonata. Other than that, Penelope is highly intelligent at everything else with the exception of spelling, pointed out in "The Spelling Bee!", where she spells quiche wrong. She seems to also wield the intellect of a natural scientist as she is able to create chemicals and properly instruct how to dissect super-naturals.
Witty, rapid-fire with sarcasm and barbed quips; occasionally breaks into nerdy aside comments; uses playful sarcasm when revealing feelings
