Complex sentence: As the episode begins, Timmy Turner is basking in the glory of being the chosen one in Fairy World, but it turns out that he isn't such a hero after all, when it becomes clear that the Darkness has returned.
Split into simpler sentences: As the episode begins, Timmy Turner is basking in the glory of being the chosen one in Fairy World. It turns out that he isn't such a hero after all, when it becomes clear that the Darkness has returned.