A person who is absolutely in love with 'The Phantom of the Opera'. The person is a little (or extremely) obsessive with The Phantom of the Opera, and knows the majority of what there is to know about it (movies and play).
I first used this term on myself when i realized that i needed something to describe how i feel about The Phantom of the Opera. And since RENT lovers (Which I also am) have the term 'Rentheads', I figured I would create the term 'Phantom Junkie'.
"So have you hung out with that new girl yet?"
"Yeah, yesterday. She's really into theatre."
"Is she really?"
"Yeah, she and her boyfriend are Phantom Junkies. It's funny, because they're just like Christine and Raoul!"