Jeff 'Swampy' Marsh. Actor: Phineas und Ferb. Jeff Swampy Marsh is an American voice actor, animator, cartoonist, singer and writer from California. He co-created Phineas & Ferb and Milo Murphy's Law alongside Dan Povenmire. He also worked on various episodes of Family Guy, Rocko's Modern Life and SpongeBob SquarePants. He is known for voicing Major Monogram, who is essentially an equivalent of Nick Fury for Perry the Platypus in Phineas...