Ramon Guevera "Sheen" Estevez is one of the two tritagonists (alongside Carl Wheezer) of the Jimmy Neutron franchise and is also the main protagonist of it's non-canon spin-off Planet Sheen. He is one of Jimmy's closest friends. Sheen's obsession with Ultra Lord is one of the running gags in the series. He is shown to have many Ultra Lord action figures, knows a lot of the trivia from the show, and wears an Ultra Lord t-shirt. His love for the superhero was noted in the original film, and was carried on throughout the course of the series.
Sheen was voiced by comedian Jeffrey Garcia.
Sheen is Jimmy's second best friend after Carl.
He is a big Ultra Lord fan. Even so to be obsessed with it. Sheen is Jimmy and Carl’s best friend, and Libby’s boyfriend. Although Libby didn’t like Sheen, they became a couple at the end.
However in Planet Sheen, his new girlfriend is Aseefa.
In Planet Sheen, he was the main protagonist of it. In the first 18 episodes of the UK Version of Planet Sheen, he has his blank flank. In the last 8 episodes, Sheen got a new shirt. In the USA's first episode, he has his blank flank. But in the last 25 episodes, he got his blank flank.
- Sheen is 11 years old.
- Sheen is of Mexican descent.
- Sheen's name (or nickname, though it gets used as his main name) and family name derive from the family of actor Martin Sheen, born Ramón Antonio Gerardo Estévez. There is arguably a resemblance between Sheen's basic design and Martin's sons, actors Charlie Sheen and Emilio Estevez.
- Sheen's talking primate companion, Nesmith, is named for musician and video artist Michael Nesmith, a member of the 1960's band, The Monkees.
- He turned into a Planet Hero when he accidentally flew into Space.