Sean Hassett, known as irregular, is a Philadelphia artist who grew up in Darby, where he first took to the word that became his name. Largely self-taught, he began making art in 2012 and has shown work in Rittenhouse Square since 2014. His interest in reflective, fragmented surfaces traces back to his grandfather's stained-glass workshop.

Hand-cut mirror is his main material, set into acrylic paintings and mosaics so that viewers see themselves in the work. He has made well over a thousand pieces. Since 2020 his "irregular" tag has appeared across the city, from West Philly to Center City.

In 2022 he painted infinite medium, a mini-mural for Wawa Welcome America with Streets Dept Walls and Mural Arts Philadelphia, shown at The Oval. Streets Dept named his mirrored street art one of the city's top street art moments that year. In 2023 he was one of four muralists in "Mural Magic" at the Philadelphia Flower Show and was featured in Hyatt Centric Center City's Maker Series. His solo exhibition "We the Youth" ran at Philadelphia International Airport in 2024–25. His 2026 mirror mosaic of LeBron James at 8th and Market was covered by the Inquirer and Billy Penn.