Cosmo Julius Cosma, normally refered to as just Cosmo, is one of the main protagonists of the Nickelodeon show The Fairly OddParents. He is the husband of Wanda, the proud father of Poof, and the godfather of the protagonist of the series, Timmy Turner. While normally presented as the idiotic, yet loving fairly godparent of Timmy Turner in the main show, there are many conspiracy theories around his true nature, and they would often present him more as a ruthless force of evil, and is merely feigning stupidity in order to get away with his heinous crimes. The following is a list of known theories that "prove" that Cosmo is truly a monstrous character.
Prior to his role as the godparent to Timmy Turner, he was shown as a fairy-in-training. Cosmo was seen destroying several civilizations by accident. For example, he was responsible for the destruction of Pompeii when he accidentally caused Mt. Vesuvius to erupt when he was trying to impress his teacher, Jorgen Von Strangle, and he had also managed to have the city of Atlantis sinked 9 times, thus earning him the title as the "Accursed One." Cosmo was also shown as being a danger to the inhabitants of Fairly World, having destroyed it several times, and he had also managed to earn Jorgen's undying hatred because of this.
Cosmo has also accidentally destroyed other planets as well. In the episode in which Vicky's evil nature was removed from her, he accidentally ignites a bomb that destroyed Pluto. However, to his credit, Pluto wasn't considered a planet anymore, and there was most likely not any life on it in the first place.
While this should make Cosmo simply a misguided idiot, many fans of the show were unconvinced by Cosmo's justifications for his actions in the past, and have come up with theories to give a bit more characterization to this seemingly incompetent fairy.
Many theorists believe that Cosmo is aware of his actions, and is merely playing the role as the idiot so that he wouldn't be punished for his crimes. Many theorists have pointed to the show in which Cosmo is either shown having the occassional burst of brilliance, or he's shown as being not as dumb as he lets on. Could it be possible that Cosmo is actually a very calculating mass murderer who is simply playing dumb because no one would expect an idiot of being capable of committing great acts of evil?