Mercutio is muttering some very unkind things in Venetian; which the mansion is gracious enough to not translate. Any hopes of hiding the blush slowly spreading across his face are gone, but he perseveres.

“Claudius,” he says, slightly higher-pitched than he means it to be. “He has only just arrived.” Would he be encouraging this nonsense if it were Romeo in this position? Absolutely. Benvolio is a different story.