Shane Acker first made 9 (2009) as a ten minute short film while he was still at UCLA. It was nominated for Best Animated Short at the Oscars, and although it didn't win, Acker was offered the chance to expand it into a feature film. It follows the same basic plot, but more characters have been added, they have the ability to talk now, and the reason for the world's destruction is explained in more detail.
1 tells 9 that he led the others to their current hideout, which he refers to as "sanctuary". The building happens to be the Notre Dame church, famously referred to as "sanctuary" in "The Hunchback of Notre Dame".
Being a Tim Burton production, some of his trademarks have made it into the film. The themes of outsiders or the alienated triumphing over adversity. Some of his design schemes are present like stripes. The funeral scene looks very similar to the one in Burton's Batman Returns (1992). And people who've worked with Burton helped make the film, like Martin Landau. The film was also co-composed by Burton's frequent composer Danny Elfman.
The Chancellor mentioned by the scientist and showed in the old archive footage appears to be a reference to Adolf Hitler, the fascist dictator of Germany from 1933 through 1945. Hitler held the title of Chancellor of Germany, until he gave himself to the new title of Führer. When standing in the car in what appears to be a parade, The Chancellor lifts his hand in a motion similar to that of The Hitler/Nazi Salute. The flags and banners shown on the wall when The Chancellor announces the creation of The Machine are similar to the Swastika Flag of the Nazi Party. Finally, when the Chancellor takes The Machine away from The Scientist, the soldiers who take The Scientist away resemble SS Officers (Hitler's Secret Police Force) in uniform and actions.
The trivia items below may give away important plot points.
The funeral scene, which is the final scene in the film is similar to the final scene of another animated film, which was also about puppets - 2004's "Strings". 9, 7, 3 and 4 attend the funeral of 1, 2, 5, 6, 7 and 8 and when 9 uses the talisman to free their souls. 7 says to 9 "They're free now." In the final end of "Strings", Hal Tara, Zita, Erito, Eike and the Zeriths attend Ghinna's funeral. When Ghinna's funeral raft sails away, Zita says to Hal Tara "She is free now, Hal. Truly free".