Wallace Worsley Jr., son of the film's director, Wallace Worsley, said that many of the extras for the massive crowd scenes were recruited in downtown Los Angeles for $1.00 a night and meals. Among them, he said, were a good number of prostitutes, who did a "considerable sideline business" on the sets. Universal also hired 50 Pinkerton detectives and put them among the crowd, and their job was to catch pickpockets and various other thieves among the extras.
Lon Chaney's makeup was the most extreme he'd had at that point in his career. A knotted wig, nose putty for warts and on the cheeks, innovative use of cotton and flexible collodion, adhesive tape, some false teeth, and a fake eye made up his visage. The final touch was a plaster hump, which, contrary to popular opinion, was only about 10-15 pounds and did not cause Chaney any back problems. The grotesque makeup took three hours to apply.
In order to prepare himself for the role of Quasimodo, Lon Chaney held interviews with people who suffered from various physical deformities. His makeup was so masterful for its time that many viewers believed that the actor playing the title character truly appeared in real life as he did on film.
Lon Chaney's salary on the film was $2,500 a week. Shooting began in December 1922 and was completed in June 1923. Chaney made close to $60,000 plus contract bonuses from the picture, which was the longest shoot in his career.
This film was the first to use intercom technology to act as a communication device between the director and his assistants during production. Western Electric provided the wireless communication. This is standard equipment on large-scale films today.