After the release of Metal Gear Solid 2: Sons of Liberty (2001), Hideo Kojima said that he would not direct this game. He wanted a member of his team at Konami to replace him, but none of them wanted to, so he was forced to change his mind and direct after all.
Ocelot's tricks with his dual revolvers, were performed by a stuntman and recorded through motion capture.
In an interview, Harry Gregson-Williams jokingly said that he might return to compose this game's music "if it's set in the Amazon". At the time, Hideo Kojima actually was planning to set it in the jungle. Kojima decided to use this as a way to get Gregson-Williams to return; he told him that what he said had been the inspiration for the game's setting. He didn't tell Gregson-Williams the truth until the music was nearly finished.
The character of "The End" (as well as the concept of The Boss being Naked Snake's mentor) was based on a scrapped member of Dead Cell from Metal Gear Solid 2: Sons of Liberty called Old Boy (sometimes referred as Oldman). Old Boy (according to the MGS2 gameplan) was a 100-year old former Nazi general who wielded a Panzerfaust as his weapon of choice and was also a mentor to several soldiers, including Big Boss himself. His character was written out of the Metal Gear Solid 2 script because they could not find a way to fit it into the story.
One of Hideo Kojima's colleagues told him about and advised him to listen to stellastarr*, but Kojima heard "Starsailor". He liked the song "Way To Fall" and chose it as an ending theme.