Carlotta Giudicelli

From Phantom of the Opera

Carlotta Giudicelli is the leading diva of the Paris Opera House

In the novel, she is a minor character hailing from Spain. She was unable to attend the farewell gala, due to her being suddenly ill (it was later explained that she wasn't actually unwell, just spoiled and temperamental). She later sings Faust and croaks like a toad

In the musical, she is a major character hailing from Italy. She is more selfish and spoiled, and she has a husband named Ubaldo Piangi, who panders to her