Jeffrey Kent "Swampy" Marsh is an American animator, voice actor, writer, director, and producer. With Dan Povenmire, Marsh co-created the Disney Channel animated series Phineas and Ferb and Milo Murphy's Law, in both of which he voiced the character Major Francis Monogram. Marsh was born in Santa Monica, California, where he grew up with a heavily blended family dynamic. Marsh is known for his contributions to the television animation industry, working for over six seasons on the animated television series The Simpsons. Marsh continued to work on other animated television series, including King of the Hill and Rocko's Modern Life, before moving to England in 1996.

Phineas and Ferb is an American animated musical-comedy television series created by Dan Povenmire and Jeff "Swampy" Marsh that aired on Disney Channel and Disney XD for four seasons between 2007 and 2015. The series follows stepbrothers Phineas Flynn and Ferb Fletcher during summer vacation. Every day, the boys undertake the construction of a grand project, or embark on a spectacular adventure, to make the most of their time on vacation. This annoys their controlling older sister, Candace, who frequently tries to expose their schemes to her and Phineas's mother. The series follows a standard plot system; running gags occur in every episode.