Penelope Lang (Catherine Disher) is Betty's self-obsessed, near heartless rival on Earth, who thinks of herself as the most popular girl at her school. Her favorite pasttime is ridiculing the other students, Betty and Noah in particular. She is rich, spoiled, and often uses her popularity or wealth to undermine Betty's social standing, a plan that inevitably goes wrongt. She is usually seen with two sidekicks named Megan and Sarah. She’s used to getting her own way — even if it means stepping all over other people. In fact, she enjoys getting her own way more if she has to step over other people to do so. In "Bracelet Yourself", she tampered with Betty's bracelet which is property of the Galactic Guardians and caused the Starcruiser to lose control. She also seems to not hate, but despise Betty enough to be violent, for in "Pre-Teen Queen of Outerspace", she attempts to kill Betty and her friends, though she thinks it is just a dream, and in "Mirror of Morgana", she kicks Betty in the face. Being Betty's rival, she also dislikes Noah just about as much as she dislikes Betty. In season three, she is occasionally seen with her grandmother Petunia, who is just about as snobbish as she is. Though she has come close to discovering the existence of the Galactic Guardians (to find out Betty's secret so she can humillate her, however, she never expects to be a Galatic Guardian), having stolen Betty's bracelet in "Bracelet Yourself", accidentally teleported into Galactic Guardian HQ in "No Space Like Home", being given a note from her future self in "The Future is Now", and even having tampered with and in Power of the Pharaoh, read out of Betty's own "captain's log" (this causes people to think that Betty is a science fiction author), she quickly dismisses all of the evidence. She doesn't believe the evidence are real.
In "The Future Is Now!", Penelope, while not a Galactic Guardian herself, is freeloading with the remnants of the Galactic Guardians. Penelope stated that if she knew Betty was a Galactic Guardian, she would have told the whole world (The reason why is unknown for now). If only her past self believes it. However, she provides the opportunity for Betty and Noah to steal the time machine back from Maximus and return to the past. She secretly gives a note to her past self to tell her that Betty is a Galactic Guardian, but the past Penelope doesn't believe it's real. The irony is that if she find out about Betty's secret and told the whole world, Maximus would have found out and come to earth. Penelope would have put Earth in danger if she did that just because she hates Betty. Also, Betty would have been more famous on Earth.
- Chaz Lang - older brother
- Queen Penelobee - clone
- Megan - minion
- Sarah - minion
- Petunia - grandmother
- Poopsie - pet cat
- Mr. Lang - father
- Mrs. Lang - mother
- Catherine Disher, the voice of Penelope, is better known as the voice of Jean Grey on X-Men: the Animated Series, as well as coroner Natalie Lambert on the live action horror-crime drama series Forever Knight. She also appeared in the long-forgotten 1986 sci-fi film, The Vindicator, where she played a scientist who gets killed by a rage-filed chimpanzee.
- In Pre-Teen Queen of Outer Space, the Bee People consider Penelope to be the most despicable female in the universe. Although, she might have a sensitive side. In The Market, she is seen crying because her cat Poopsie died.