Esmeralda is Quasimodo's pet rat and an antagonist of Hotel Transylvania. She is always accompanying the great chef.
Later on in the film, she and Quasimodo are search for Jonathan, plotting to capture him and turn him into human pot pie. The two succeed in kidnapping Jonathan and drag him off to the kitchen to cook him. Dracula comes and saves him, and again, tries to convince Quasimodo Jonathan isn't human. Quasimodo says he'll believe him if Jonathan scares Esmeralda. Jonathan tries and fails, being scared by Esmeralda himself. Dracula frezzes Quasimodo and leaves him.
Esmeralda then appears as Mavis' party, her and her master planning to reveal Jonathan is in fact human. While at first, the other monsters don't believe them, Esmeralda attacks Jonathan, showing that he is a human. Her final fate is unknown.