Jeffrey Kent "Swampy" Marsh (né Dudman;[1] born December 9, 1960)[2][3] is an American animator, voice actor, writer, director, and producer.

With Dan Povenmire, Marsh is the co-creator and co-star of the Disney Channel animated series Phineas and Ferb and Milo Murphy's Law.

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.

After six years living in England, Marsh was asked by his longtime partner Dan Povenmire to help produce Phineas and Ferb in 2007, a concept the two had while working together on Rocko's Modern Life.

[4] Marsh spent his summer vacations being active, going outside and digging trenches and tunnels, building tree houses, and constructing forts.

[3] To help him with his animation efforts on the show, Marsh utilized several books about art, architecture design, and artistic rendering which he kept in his household library.

[9] His desk in the series' office placed him opposite of fellow layout artist Dan Povenmire; the two bonded over shared tastes in humor and music and quickly formed a friendship.

[5] By 1993, Marsh was working as a writer and director on Nickelodeon's animated series Rocko's Modern Life[3]— the channel's first "in house" cartoon production[10][11][12]— for four seasons.

[3][14] In 1996, Povenmire and Marsh conceived the series Phineas and Ferb,[15] based on their similar experiences of childhood summers spent outdoors.

"[17] Marsh spent six years in the city,[3] working on several animated television productions which included Legend of the Dragon, Postman Pat and Bounty Hamster,[17] along with other projects produced by major companies BBC, ITV, and Carlton TV.

[13][17] The pair still needed to convince overseas Disney executives to pick up the series, so instead of a conventional script, they recorded the storyboards for "Rollercoaster".

[7] A third Emmy nomination, for the episode "The Monster of Phineas-n-Ferbenstein" (2008),[22] pitted the show against SpongeBob SquarePants,[23] although neither nominee received the award due to an unspecified technicality.

[28] Marsh and Povenmire collaborated again and produced a series for Disney XD titled Milo Murphy's Law, which premiered on October 3, 2016.