Penny first appears as a cheerleading squad to celebrate the school's opening day and welcoming the freshmen.
After Will becomes popular, she eventually shows her true colors being sarcastic, rude, arrogant, and mean. She then uses her clones to keep his "Sidekick" friends from sitting with them.
During homecoming, she teams up with Royal Pain, Lash, Speed, and Stitches to turn all participants into infants. She, along with Lash and Speed, later catch the six sidekicks in the hall, and chooses Layla as her opponent. Her ignorance of Layla's true power becomes her weakness when she punches her in the face. In anger, Layla defeats her and her clones by turning the cafeteria into a rainforest and immobilizing them. After this, Penny reveals Royal Pain's plan to sabotage Sky High and stop it from floating. However Layla and the others manage to foil her. She is later seen locked up in the detention room along with her group by Principal Powers to prevent them from escaping (since the detention room negates anyone from using his/her powers).
At the end, it is revealed that Penny and the others are in prison. She is seen still using her multiplication powers.
Powers and abilities
Penny's power is to replicate herself. Aside from replication, she is also very athletic, which serves as a trait in battle. She has enough power to create an entire cheerleading squad, which also works as a team.