Actor Existence Failure: Phillip Seymour Hoffman died just a week before he would have finished filming his scenes for the two Mockingjay films. The studio is keeping mum about how this will affect them.
The film was banned in Vietnam. Officially, the ban was for showing youth violence, though it has more to do with Vietnam not being happy with a film that shows youngsters fighting back against a totalitarian state.
Strangely enough, the film was not banned in China itself, despite it being more authoritarian than Vietnam. This is possibly due to it being possible to interpret the film as a parable about "Western decadence".
At first, the film's creators considered casting an actual teen in the lead role (among others, Saoirse Ronan, Chloe Moretz, and Hailee Steinfeld were considered for Katniss' part). They finally settled with 21-year old Jennifer Lawrence to play 16-year old Katniss. Liam Hemsworth (Gale, 18) was 21 during filming, while Josh Hutcherson (Peeta, 16) was 19. Leven Rambin (Glimmer, 18) was 21 at the time.
Averted by Isabelle Fuhrman (Clove), Jacqueline Emerson (Foxface), Amandla Stenberg (Rue), and Willow Shields (Prim), aged 14, 16, 12, and 11 during production.
How about Brazil: Izzy has to fight for her life after entering a fight to the death. In the sequel, she meets other tributes, including Wyldstyle (from District 1) and Luanne Platter (from District 7).
The Other Darrin: In the Japanese dub, possibly due to licensing, Rue and Seneca's roles are recasted in the DVD/BD release of the movie in Japan, but the rest of the cast keeps their original dub voices from the theatrical version.
Throw It In: The extra scenes with President Snow and Seneca Crane are apparently the product of a lengthy letter Sutherland wrote to the director on his interpretation of the character of Snow after he read the original screenplay. Ross liked them so much that he wrote two scenes of character exposition exploring the themes of Sutherland's letter and added them to the script for the first movie, thus elevating Sutherland to the status of Cool Old Guy in real life. You can find his letter online, but the DVD special features has him actually reading it.
Working Title: The working title of the first novel was The Tribute of District Twelve. Some foreign editions do this, like the German release, Die Tribute Von Panem(The Tributes of Panem).