Seth is a boy that Uncle Grandpa visited as seen in the episode Messy Bessy. He is voiced by Kari Wahlgren.
Seth is a young boy who has blond yellow hair, he wears a orange shirt and light blue shorts, he also wears blue and white sneakers.
Seth is a bratty little boy who likes to talk slang like saying "yo" and "that's whack son". By listening to Trashy D.'s music, Seth doesn't have much care in the world or for his parents, he acts like a rebellious teenager. Until Messy Bessy nearly ruined his life, Seth appreciates simple chores like cleaning his room, and he has more respect for his parents with the help of Uncle Grandpa
An artist of Seth's beatpod is named "Blue Group", this is referencing the Blue Man Group.