Approximately a hundred Kaijus and a hundred Jaegers were designed, but only a fraction of them appeared in the film. Every week, the filmmakers held a vote for their favorites.
(At around 1 hour, 25 minutes) The inside of the building that Gipsy's fist smashes through was created using miniatures. Many of the components of the office cubicles were made using 3-D printers. The lighting was practical and done to scale. Once the set was ready, a large green mandrel was rammed through it. This was digitally replaced with Gipsy's fist.
Though the giant monsters were always intended to be computer generated, all of their designs were expanded from the notion that they could be "worn as suits," like in traditional kaiju films.
According to Travis Beacham, in an earlier version of the script Mako and Raleigh spoke two different languages for a majority of the film. After connecting as pilots, they slowly began to understand one another, and before the end they heard each other speaking in their own respective languages. The only remnant of a language barrier is when Raleigh speaks to Mako in Japanese, and she is surprised he knows her home language.
Screenwriter Travis Beacham also wrote the graphic novel Pacific Rim: Tales from Year Zero. Released along with the movie, "Tales from Year Zero" serves as a prologue to the film and is set twelve years before its events.