o.g.
OG stands for Opera Ghost, the creepy ghost who lives under the opera house and scares people with his face and his love for singing.
@PhantomFan: The Opera Ghost is the OG of the opera world. He’s loud and creepy.
Opera Ghost: I love singing. I also love making people scream.
The Phantom of the Opera: I'm not just a ghost. I'm an OG.