Final answer:
Megamusicals are high-budget, commercially successful sung-through theatre productions known for their spectacle and reliance on set design and special effects. Having become prominent in the 1980s with shows like Cats and The Phantom of the Opera, they represent a significant aspect of the Broadway industry.
Step-by-step explanation:
An entirely sung-through show, these megamusicals are the commercial 'cash-cows' of the Theatre industry. Productions like The Phantom of the Opera, Evita, and Miss Saigon are elaborate examples of this genre. With large-scale productions, they are expensive to produce and rely heavily on set design, choreography, and special effects, often becoming blockbuster extravaganzas.
The 1980s saw the emergence of the megamusical with shows like Cats and Les Miserables, capitalizing on spectacle and commercial profits and changing the face of Broadway. These shows require major investments and can take years before they break even, despite often running to full houses. The shift toward more socially relevant stories began in the 1990s, yet the appeal of the megamusical continued, demonstrating the power of musical theatre in the Broadway industry.