In this episode, Martin mentions how he doesn't like or understand opera. In real life, John Mahoney (Martin) was a fan of opera and wine, while David Hyde Pierce (Niles) wasn't a fan of either.
In this episode, after a night at the opera watching "Rigoletto" by Giuseppe Verdi, Frasier (Kelsey Grammer) remarks to his date that the finest soprano to sing the role of "Gilda" was "the great Matilda de Cagny". Mathilde de Cagny was the animal trainer who owned Moose, the dog who plays Eddie.
Martin criticizes the opera he and Frasier are about to see, saying it's goofy because everyone is pretending to be someone they're not. This is exactly the farce that plays out when they return home afterwards.
Marty Crane makes fun of the English. John Mahoney, who plays Marty, was born in England so he was actually insulting himself.
Frasier compares the soprano (off screen) to Renata Tebaldi, which Martin repeats to the mother, as though Tebaldi had sung the role of Gilda. She did not.