Which word best describes something that is broadly or extravagantly humorous?

The word that best describes something that is broadly or extravagantly humorous is "farcical." This term refers to a style of humor that employs exaggerated, improbable situations and ridiculous events, often aiming to provoke laughter through its absurdity. In the context of the question, "farcical" captures the essence of humor that is not only exaggerated but also theatrical, leading to an overall sense of enjoyment and amusement.

In contrast, the other options do not convey humor effectively. "Serious" denotes a lack of humor and a focus on weighty or important matters, which stands in stark opposition to the concept of extravagantly humorous material. "Monotonous" suggests dullness and repetitiveness, which can never be associated with humor. Lastly, "melancholic" describes a state of sadness or sorrow, which is entirely contradictory to the idea of something being humorous. Thus, "farcical" is the most fitting choice for describing something that is broadly entertaining and humorous.