The Phantom "borrowing" the AIAOY motif
So when they're performing Don Juan Triumphant, after the Phantom has been revealed to everyone, he goes off-script and appeals to Christine by paraphrasing a verse from AIAOY.
Now, this isn't part of the opera anymore, so presumably in-universe he's not actually singing. What do you think is happening here?
Do we just hear it as the same tune because it's the same emotions being expressed? Or is Erik deliberately cribbing Raoul's delivery in some in-universe way because, hey, it worked when Raoul did it...
Or do you take this all as a heightened fantasy universe where the characters are aware they're singing?
Not like this is the only musical to use motifs like this, but this one just tickled my brain a bit lol