One day, Count Duckula, Igor and Nanny decide to visit the opera house in Paris. Little do they know that it is during this exact time that 'The Phantom of the Opera' is planning to take his revenge on the opera house and all those who visit it. The Phantom, with the aid of his assistant Krool, is plotting to make sure that his music "is the last thing they ever hear".
Inside the opera, Igor bumps into his old friend and colleague Krool. Krool informs Igor that he is working for the Phantom and warns him to leave immediately because his master "is planning something so wicked, so fiendishly evil" that it makes even his blood turn cold. Krool's master, the Phantom, is planning to kidnap "the prima donna, the great Elvira" so he can take her into his lair in the sewers and force her to sing one of his compositions. During the opera's interval Duckula notices that Igor is missing. Duckula doesn't know that Igor has joined the Phantom so he can help him and Krool carry out his sinister plan and tries to find him. Noticing that Duckula and Igor are not in their box anymore, Nanny also goes searching for her beloved Duckula.
Under the cover of darkness, the Phantom kidnaps Elvira and runs away to his lair with Krool and Igor. When they arrive at the sewers, the Phantom reveals the full extent of his plan. As soon as Elvira sings and hits the "Top C" note, a bomb will detonate, killing everyone inside the opera house. Igor likes the plan at first but realizes that he must warn his true master, Duckula, so he can leave. However, the Phantom does not want Igor to leave and forces Krool to tie him up. Later, the Phantom realizes that they had kidnapped Nanny instead of Elvira by mistake, who was on the stage trying to find Duckula. When the Phantom hears Nanny terrible singing he decides that he is beaten and runs away to the Grand Ole' Oprey House in Nashville (United States of America) to become "The Phantom of the Oprey".
- This episode is based on 'The Phantom of the Opera', a novel by French writer Gaston Leroux. The story has been successfully adapted into various stage and film adaptations.
- Krool's character is based on that of Peter Lorre, who was an Austro-Hungarian-born American actor. Lorre featured in many Hollywood crime and mystery films and was frequently typecast as a sinister foreigner.
- The Grand Ole Opry is a weekly country music stage concert in Nashville, Tennessee. It is fitting that the Phantom runs away to the Grand Ole' Oprey House in this episode since Nashville is referred to as "Music City" in the United States of America.
- Count Duckula, Igor and Nanny have an entire box to themselves in the opera house. In a traditional opera house, the auditorium is U-shaped. Around the auditorium are tiers of balconies, and often, nearer to the stage, are boxes (small partitioned sections of a balcony).
- Duckula describes himself at one point as "an opera buff".
- When Nanny mistakenly thinks that the opera is over, she says that it was "hardly worth getting all dressed up for." However, she is dressed in the same clothes as usual. Only Duckula is dressed a little differently since he had brought his top hat with him.
- The Phantom of the Opera has only one eye, which is red in colour. When the Phantom closes his eyes, it almost appears as if he has no eyes at all because of his mask.
- The extras accompanying the prima donna Elvira on the stage are dressed like Egyptians. They look very similar to the characters Hoomite and Yoobee in the first episode, 'No Sax Please - We're Egyptian'.
- Duckula's box at the opera has the superstitious number 13.
- The name of "the prima donna, the great Elvira" might be based on the protagonist of the 1988 American comedy film, 'Elvira: Mistress of the Dark'.
- The crazy credits for this episode feature the conductor Phil R. Monik, a pun on the word 'philharmonic'.
- Narrator: "Here, at the magnificent opera house in Paris, glittering halls await the throng of glittering music lovers but far below, in the very sewers which flow beneath this beauteous building a more sinister song can be heard."
- Nanny (after Duckula says he is going to escort them to their box): "A box? Oooooh, you'd think a place as grand as this would have proper chairs, wouldn't you?"
- Krool: " Igor! My old fiend! I mean, friend!"
- Igor: "Evil? Did you say evil? Oh, how it does my heart good to hear that word."
- Igor: "If only my master was half as malevolent as his father, or his father's father!"
- The Phantom of the Opera: "My evilness doesn't need checking. It is in perfect working order."
- Igor: "Well, it's like this Mr Opera."
- Igor (referring to Duckula): "It is my duty to protect the Duckulas, even that one."
- The Phantom: "Yes, Krool. You stupid, useless, bumbling, idiotic, fat-headed... (after Krool reminds him) dolt!!!"
- Duckula: "Oh, there you are Nanny. I thought I recognized those dulcet tones."