Trivia

Co-Writer and Director Bong Joon Ho and the designer of the creature nicknamed it Steve Buscemi, based on the actor's screen persona and the way he acted in Fargo. Secuestro voluntario (1996).

The event described in the beginning of the film is based on an actual event. In February 2000 at a U.S. Military facility located in the center of Seoul, a U.S. Military civilian employee named Mr. McFarland was ordered to dispose of formaldehyde by dumping it into the sewer system that led to the Han River, despite the objection of a South Korean subordinate. The government attempted to prosecute Mr. McFarland in court, but the U.S. Military refused to hand over the custody of Mr. McFarland to the South Korean legal system. Later, a South Korean judge convicted Mr. McFarland in absentia. The public was enraged at the government's inability to enforce its law on its own soil. In 2005, nearly five years after the original incident, Mr. McFarland was finally found guilty in a court in his presence. However, he never served the prison sentence, and there have been no sightings of a mutant creature in the Han River - yet.

As of March 2009, this is the highest grossing film to date in South Korea, selling a total of 13,019,740 tickets. This means that over twenty percent of the South Korean population watched the movie (although there were also some who went to see it several times). The film was such a cultural phenomenon that a statue of the film's creature was eventually erected on the bank of the Han River.

(at around 24 mins) The scene where Nam-il kicks Gang-du at the funeral ceremony was improvised.

Bong Joon Ho has expressed some frustration when making the film by stating that, "When you first think of making a monster movie you have to realize that a lot of people may be down on you because there is a big prejudice against such films." He mention that after he conceived of the idea and told his friends about it, they looked at him like he was crazy and told him, "Don't do it, don't waste your talent". Bong Joon Ho was disheartened by these comments, which he described as "little wounds to the heart" and was motivated to write the script in secret.