The guitarist, who appears early in the film and also at the Georges Méliès party near the end, is modeled after famed Belgian guitarist Django Reinhardt. The filmmakers even went so far as to have the actor's left hand match Django's: that is, he doesn't use his fourth and fifth fingers (they were burned in a fire).
The cam mechanism in the automaton is heavily inspired by the machinery in the Jaquet-Droz automata, built between 1768 and 1774. Indeed these automata are still in working condition (they can be seen at the Musée d'Art et d'Histoire of Neuchâtel, in Switzerland) and are capable of drawing figures as complicated as the drawing depicted in the film. Many nuances such as the head following the pen as it was drawing and dipping the pen in ink were also present in the automata in real life.
In flashbacks we see Georges Méliès staging his productions with lavishly colored sets and costumes. The real Méliès only used sets, costumes and make-up in grayscale, since colored elements might turn out the wrong shade of gray on black and white film. Many of the prints were then hand tinted in post-production.
The music during the scene in which Hugo and Isabelle read in the book The Invention of Dreams about the history of film making is Danse Macabre by Camille Saint-Saëns. He is considered to be the first composer ever to write an official movie soundtrack for The Assassination of the Duke de Guise (1908), making this musical reference quite apt.
Robert Richardson's win on the Oscar's cinematographic category for this film meaning that he, Emmanuel Lubezki and Vittorio Storaro are the only present living cinematographers to win the award 3 times.
The driving force behind the film was Martin Scorsese's young daughter Francesca Scorsese who presented him a copy of the Brian Selznick book as a birthday gift hoping that he would make a film out of it someday. It was also her suggestion to have the film presented in 3D format. Rather than having the 3D accomplished by post-conversion, Scorsese decided to have it shot in native format, so together with VFX supervisor Robert Legato and cinematographer Robert Richardson, they spent (before filming) about two weeks at the Cameron/Pace group doing a crash course on filming in that format.
There are several references to James Joyce in the movie. In the beginning he is standing in the café. Also, the frozen people outside of the apartment building are a direct reference to Joyce's short story "The Dead", which has the central character imagining frozen people in the snow all over Ireland.
This Martin Scorsese movie won the same number of Academy Awards as Scorsese's The Aviator (2004) totalling five. Both were nominated for Best Picture and Best Director Oscars but lost out. The film also won the same number of Oscars in the same year as The Artist (2011). Both films examined silent cinema.
When Hugo shows Isabel the clock passageways, she says "I feel just like Jean Valjean!" Jean Valjean is the protagonist in the Victor Hugo novel "Les Míserables". Sacha Baron Cohen who played the policeman in this film, played the con man Thernardier who bothers Jean Valjean in Les Misérables (2012).
Martin Scorsese sent screenwriter John Logan the book The Invention of Hugo Cabret by Brian Selznick. When John Logan began reading the book he completely understood why Martin Scorsese was interested in adapting it.
The trivia items below may give away important plot points.
The train station depicted is the Gare Montparnasse. The real life Georges Méliès did in fact work as a toymaker at that station after World War I. The derailment scene during Hugo's dream is a reference to the famous 1895 derailment at the station.
In the very last shot of the film, of the automaton, the costume designers made a little tuxedo for the automaton to wear because the very last scene is a party and the costume designers felt that the automaton should be dressed up just like everyone else. Martin Scorsese decided against this because he wanted the audience to see all of the gears of the automaton at the end.