He is voiced by Thomas Middleditch, who also voices Harold Hutchins.
Penn is at a normal height with curly red hair and cyan eyes. He wears a white-with-black-sleeves shirt with a white slashed zero outlined with orange on the front, a blue plaid collar and end of sleeves, and a silver neckline and sleeves. Around his hips, he wears a black belt with a belt buckle, a silver circle with a glowing bright blue shape in the center. He also wears red skinny jeans and boots with black fronts, white backs, and a yellow line above the ankle.
Penn's parents Vonnie and Brock Zero worked as part-time heroes that saved their world and other worlds using the Multi Universe Transprojector. However, when they got stuck in the "Most Dangerous World Imaginable", Penn inherited the job of a part-time hero from them and moved in with his Uncle Chuck and Aunt Rose. When not going to school, he and his pals Sashi and Boone dimension-hop to places that need help and battle Rippen and his minion Larry.
- Penn sleeps with a teddy bear, as revealed in "The Princess Most Fair".
- In "The Old Old West", Penn is shown to be able to fix his scooter while talking to his parents.
- In "I'm Super!", Penn reveals that he had always wanted to be a superhero since he was six years old.
- In "Lady Starblaster", Penn is a talented dancer, knowing many styles of dance and having won Middleburg's Snazziest Feet Award three times running.
- It's revealed that in "The Ripple Effect", his family has never failed a single mission, hence why their last name is Zero.
- As shown in "Rip-Penn", whenever he loses his patience, he loses his temper as well.
- Also in the same episode, it's revealed that he is afraid of sock puppets and dying (with the latter being developed after nearly dying in "Totally Into Your Body").