Ramon Guevera "Sheen" Estevez is one of Jimmy's closest friends and one of the main protagonists in the television series. 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, and knows a lot of the trivia from the show. His love for the superhero was noted in the movie, and was carried on throughout the course of the series.
Sheen is not the brightest bulb on the Christmas tree, but what he lacks in smarts he more than makes up for with his appetite. Sheen is obsessed with the Ultra Lord action hero. He collects all the Ultra Lord action figures and quotes him daily.
His romantic interest is Libby Folfax, and his interest in her became highly noticeable towards the end of the first season of the series, but in the new spin-off series "Planet Sheen", he has a new romantic interest, a blue alien named Aseefa.
Sheen is a turbocharged, hyperactive child with an attention span of 0.4 seconds. His best friend back home is boy genius Jimmy Neutron. He's got a passion for life, TV, guacamole, and a superhero called Ultra Lord. He isn't the best student, but what he lacks in common sense and focus, he makes up for in burning curiosity and loads of energy. One day, disobeying Jimmy's specific instructions ("Sheen, Do Not Touch This Rocket!"), Sheen touches a rocket and goes flying into deep space. He lands on a strange planet called Zeenu, where the grand leader thinks that Sheen is destined to bring peace, prosperity, and eternal joy. After the Emperor promotes Sheen to be his #1 Royal Advisor, Sheen gets to do virtually whatever he likes, such as battling man-eating creatures and throwing wild parties. Even when the evil villain Dorkus tries to destroy him, Sheen's crazy ways almost always save the day. He doesn't seem at all worried about whether he'll get back to Earth or not.