Conversation so far:
What are some of the references made in the film Hugo?
The film Hugo makes references to Georges Méliès' profession, the Theatre Robert-Houdin, which he owned, and the demonstration of the Lumière brothers' camera which made him interested in film.
What events happened in the film Hugo?
In the film Hugo, Georges Méliès was forced into bankruptcy, his film stock was melted down for its celluloid, and he became a toy salesman at the Montparnasse station.
What is the Le voyage danes la lune?
Many of the early silent films shown in the movie Hugo are Méliès's actual works, such as Le voyage dans la lune from 1902.
What other references are in the film Hugo besides Le voyage danes la lune?
Several viewings of the film L'Arrivée d'un train en gare de La Ciotat are portrayed in the film Hugo, depicting the shocked reaction of the audience
What watches has Henri Maillardet made?
Henri Maillardet was a Swiss watchmaker.
What time period were the historical references in the film Hugo from?
The film Hugo has French film references:  L'Arrivée d'un train en gare de La Ciotat from 1895 and Le voyage dans la lune from 1902.
Were there any other notable references in the film Hugo besides L'Arrivée d'un train en gare de La Ciotat and Le voyage dans la lune?
Emil Lager, Ben Addis, and Robert Gill make cameo appearances in the film Hugo.

Question: How were their cameos carried out in the film?
Self-contained rewrite: How were the cameos of Emil Lager, Ben Addis, and Robert Gill carried out in the film Hugo?