Jeff "Swampy" Marsh is an American animator, writer, and voice actor, best known for co-creating the popular animated series Phineas and Ferb alongside Dan Povenmire. He has worked in the animation industry for several decades, contributing to various projects and shows. In addition to his work on Phineas and Ferb, Marsh has lent his voice to several characters, including Baljeet and Perry the Platypus. His creative talents have earned him recognition and awards, making him a prominent figure in children's entertainment.