Final answer:
The letter received by Dr. Horrible reflects the 'Call to Adventure' stage of the Hero's Journey.
Step-by-step explanation:
The subject of the question
The subject of this question falls under the category of English.
The stage of the journey reflected
The letter received by Dr. Horrible from Bad Horse challenging him to prove his evilness in order to be inducted into The Evil League of Evil reflects the Call to Adventure stage of the Hero's Journey. This stage represents the initial invitation or introduction to the hero's quest and sets the story in motion.
Examples and explanation
In 'Dr. Horrible's Sing-Along Blog,' Dr. Horrible is presented with a challenge that leads him to embark on his journey to become part of The Evil League of Evil. This challenge represents the 'Call to Adventure' because it calls him to action and initiates his quest to prove his evilness.