And now back to your regularly scheduled Roommates. Please forgive me if I'm slow in answering comments; I'm a little backed up from Halloween, still.
At this point, I've seen so many versions of Erik's possible last name that I think I accidentally combined a bunch of them. Apologies.
Erik and Christine belong to Leroux and Webber.
Tracy Turnblad belongs to Waters, Shaiman, and Wittman.
Lyrics used in third panel from the Ken Hill version of Phantom. (Gorgeous song, find it on YouTube.)