Elijah Price: Now that we know who you are, I know who I am. I'm not a mistake. In the comics, you know how you can tell who the arch-villain is going to be? He's the exact opposite of the hero. And sometimes they're friends, just like you and me. I should have known way back when. You know why, David? Because of the kids. They called me Mr. Glass.
When Bruce Willis is looking at his old high school news clippings you see a professional baseball score on one of the newspaper clippings. The game was Pittsburgh vs. Arizona Diamondbacks. The Diamondbacks were not a team yet when he was in high school.
Another comic book reference: they both have signature colors. Mr Glass' color is purple (his clothes, the envelope he leaves on the windshield, interior of his house, etc.) while David's is green (all of the interior in his house, his raincoat, his suit on the train etc.).