... although I'm willing to share that I'm one of the characters of tPotO.

Maybe some of the nomenclature I found while using my Google-Fu:

Phan: A fan of one of the many versions (usually the Andrew Lloyd Webber musical) of Phantom Of The Opera. (via Urban Dictionary)
I take it the Cast is the people who are terrorized by the Phantom during the story.

Red Death: "Erik, the Phantom, attends a ball dressed as the Red Death with the inscription "Je suis la Mort Rouge qui passe!" ("I am the Red Death that passes" ) embroidered on his cloak in gold." It's based on EAP's short story (as Isaac said). The story follows Prince Prospero's attempts to avoid a dangerous plague known as the Red Death by hiding in his abbey.

If there are any Watcher/Cops/Trackers/whatever out there: the description of the Red Death (and thus Erik) is thus. The skull mask is an important feature, but since we're all wearing masks...

The term Masquerade is mentioned in the 2004 movie synopsis: this is halfway through the 2004 movie: "3 months later, we see that the Opera House is in full swing without any appearance from the Phantom since he disabled Carlotta's voice. The Opera House is holding a Masquerade to celebrate." The Phantom interrupts the Masquerade (I think this is the moment he appears as the Red Death) and presents a new Opera he has written called Don Juan. This sets the final act in motion. (Note the mention of "3 months".

(Note, in the 1910 novel, Erik dies in the end "of a broken heart" three weeks after the events of the novel. In the 1925 movie, Erik dies at the end by being thrown in the Seine by an angry Mob (that would be us ). In the Musical and the 2004 movie, the Phantom vanishes before the Mob can Lynch him.)

Interesting, when Googling I came across several sites mentioning the "Secret Plot" or "Hidden Plot". Here is some information, no time to go through it right now, but this little snippet is interesting: "Basically, we hidden plot unravelers feel we've unmasked a deeper story - a hidden story with an alternate ending where Christine marries her Angel of Music and he goes to live in the light with her." Not even sure if it's at all relevant, as it's app about the 2004 movie alone.

Another interesting tidbit: if I understand correctly, in the 2004 movie, the lover/fiancee/future husband of the female lead, Christine, finds out that she actually loved Erik, not him. In the 1910 novel and the 1925 movie, it was Erik releasing Christine as he realized she didn't love him. In the Musical, Christine was released, because she showed compassion to Erik, not love. This implies that Christine might actually be one of the Phans, but only if we are in the 2004 movie world. I agree it's a bit far out, but I thought I should mention it. (If only to have you bow to my Google-Fu )