This is why you shouldn’t have the comic relief as the main and titular character of a spin-off (most of the time, that is).
An Obnoxiously Idiotic & Unfunny Wannabe-Hero
Media of origin:
Sheen Estevez is one of the main characters in the 2001 Nickelodeon movie, Jimmy Neutron: Boy Genius, the 2002 Nickelodeon series The Adventures of Jimmy Neutron, Boy Genius and the titular character of its 2010 spin-off series Planet Sheen.
Sadly, he got badly flanderized in his own spin-off show.
Why He Was an Ultra-Flop
First and foremost, he has been badly flanderized from a nerdy, hyperactive, wacky, dimwitted, and hilarious goofball, and has turned into a completely annoying, obnoxious, self-centered and immature idiot. He barely has any personality as well, and it resembles that of Jar Jar Binks.
His humor and gags have gone from being actually funny and intelligent to being unfunny, stupid, and gross. It gets to the point that he overuses toilet humor in the worst way possible.
He doesn't even have concern about returning to Earth throughout the series. In fact, he decides to stay on Zeenu in the series finale.
However, in "Tommorrow Boys", an episode from the original series, it's implied that he did return to Earth. However, only he could make that happen, so he could likely stay on Zeenu forever.
He has completely forgotten about Libby. Instead, he has become attracted to an alien named Aseefa, which means that he has cheated on her.