Penn Zero obtained the job as part-time hero when his parents, Brock and Vonnie Zero, found themselves trapped in the "Most Dangerous World Imaginable", with no way to escape but enough experience to stay alive. From then on, he lived with his Aunt Rose and Uncle Chuck, and could communicate with his parents via the Multi Universe Hologram Uplink (MUHU). As a part-time hero working for Phyllis, he is joined by his best school friends Boone and Sashi to hop through dimensions using the Multi Universe Transprojector to foil the plans of his art teacher Rippen and the Principal Larry.
Calling her the smartest and toughest of girls, Penn appreciates Sashi's friendship and assistance. He relies on Sashi heavily when it comes to pulling off complicated tasks like retrieving the magic sword and escaping the prison cage in "North Pole Down". Whenever Sashi's being more aggressive, Penn is terrified by her, like when she wasn't pleased with his trick in dodgeball in "3 Big Problems", but at other times he enjoys making fun of her like when she gets a silly form or he's not fazed by it. He calls her out for being so violent, stubborn, and a bit crazy in "The Princess Most Fair", but when she admits she feels left out of Penn and Boone's close bond, he reassures her that she is the glue to the group, keeping the team on the rails.
In "Zap One", it's revealed that he initially wore a blue-green sweater before he had his trademark shirt and fake chain mail mesh, which were gifts that he found from his parents after his first mission. Moreover, his MUHU was also a gift from them.
Penn Zero as he appears in the Disney XD game Hero Trip
Penn and Sashi share their first kiss in the series finale, "At The End of the Worlds"
Penn Zero: Part-Time Hero (Opening Theme) • We're Breaking Out of Here for Christmas • Time to Kill • We Can Catch the Milkman • What is a Princess? • Pigoilet • Victory is Mine at Last • The Truth of It Is • Moonlight Bright • This is a Real Song • Boone Reads On • Race to the Top • Race to the Top (reprise) • You're a Karaoke King • High in the Sky • Breath In, Breath Out • Bad Weed • Today is the Day • My Name is Penn Zero • Save the Worlds • In the Splishy Splashy Sea • Come Aboard with Me • Training to Win • Wings of Destiny Song • Sometimes We Need a Friend • Build and Backup Now • The Time Table • Everybody Chillax • Why Won't You Turn Green • It's the Best Friend Song • It's the Best Friend Make Up Song • Grinkon's Song
Middleburg • Middleburg Central High • The Odyssey • Fish Stick on a Stick • North Pole • Knight World • Superhero World • Arabian World • Plush Toy World • Clown World • Dinosaur Cowboy World • Cereal World • Old English World • Giant Monster World • Zombie World • Space World • Ocean World • Color World • Musical Fairy Tale World • Caveman Spy World • Future Barbarian World • Ultrahyperball World • Demon World • Alien World • Galaxy World • Temple World • Dragon World • Gothic Mystery World • Plant World • Animal Barbarian World • Toy World • Outer Space Court World • Robot World • Pirate World • Fairymania World • Steampunk World • Ball World • Ghost World • Rock, Paper, Scissor World • Beast World • Anime World • Sitcom World • Nothingness • Most Dangerous World Imaginable • Least Dangerous World Imaginable
Multi-Universe Hologram Uplink • Multi-Universe Transprojector • Pigoilet • The QPC Unit • Vortex Tops • Specs