They first appear in Danger Wears a Cape where they are seen throwing different items at the penguins until Alice tells them to cause pain somewhere else. It was their backpack that contained the comic books.
In Operation: Neighbor Swap, Julien ends up attacking the twins, believing them to be giving him tributes. They appear again in Pets Peeved as the main antagonists of that episode as they seem to torture The penguins and The lemurs. They also seem to be part of a rich family and have lawyers.
In Night of the Vesuviuses, the dastardly twins came to an annual camp-out event at the zoo to torment the animals all night. Formerly planning vengeance, the penguins were persuaded by Private that even the Vesuvius Twins don't deserve revenge. Touched by Private's words, Skipper and the other penguins spend the night protecting the twins from the other animals. In the morning, the Vesuvius Twins realized how mean they were to the animals and reveal they never looked at it that way. They pledge to stop being mean to animals, however they start being mean to people instead.
In terms of personality, the Vesuvius twins are cruel, spoiled, and sadistic.
- The twin brothers are named after the legendary volcano Mt. Vesuvius.
- They presumably make a turning point in Night of the Vesuviuses. However they retain their cruel behaviour.