Raiden (雷電) in english means "thunder and lighting" or "thunder god." The character shares this codename with the Mitsubishi J2M Raiden, also known by the allied forces as "Jack," this was an Imperial Japanese fighter aircraft used in World War 2. The patriots had named Raiden after the plane and later let him know that, just like his name, he was simply a weapon, a tool to be disposed of once it completed its purpose.

In the original design document, it was possible for the Spoiler:hostages to die after Metal Gear Arsenal was activated. Around 50-60 bodies would have been able to be seen in the water, with the water being red from their blood, which in turn attracted sharks into the area. Both Snake and Raiden would have to go through the area afterwards.

In the hostage room on the B1 floor of the Core in Cell 1, hitting the hostages enough times triggers an angry call from the Colonel and Rose. This also causes the player to be unable to save the game by calling Rose.

According to Hideo Kojima in the documentary Metal Gear Saga Vol. 1, the game's original setting would have revolved around nuclear weapon inspections in Iraq and Iran. The plot of the game involved Solid Snake stopping the new Metal Gear while it was located on an aircraft carrier within a certain time limit. "Liquid Snake" and his group were supposed to be defeated by Snake, which would imply that Liquid would have faked his death from FOXDIE in "Metal Gear Solid (1998)". However, after working on the project for 6 months, tensions began to rise in the Middle East, so the team decided to scrap it in order to avoid controvesy. The final result of this original plot we relegated to the game's opening, involving "The Tanker".

During the Tanker mission, if Snake saves his game, Otacon will try to recite proverbs like Mei Ling in Metal Gear Solid, except he will always mess them up. If you save your game and listen to Otacon's increasingly disjointed advice 13 times, a final codec call will be shown where in the middle of Otacon reciting a proverb, Mei Ling will enter the call via an audio-only transmission and interrupt him. She tries to correct him with a misplaced "cheat sheet" she made for him, and then scolds him for losing the sheet and butchering proverbs with his own interpretations. Mei Ling will then tell Snake the correct meaning of the proverb, tell Otacon they have unfinished business, and leave the call. This is Mei Ling's only appearance in the game.

During the Plant chapter, several Mo'ai statues can be found in different locations on the Big Shell:
• Strut D: Among the scaffolding above the pool.
• Shell 1 Core, B2 Computer Room: Underneath the south-western computer desk.
• Strut L: In the far corner of the small room behind the windows.
• Shell 2 Core, 1F Air Purification Room: In the vents, using the Nikita.
• Shell 2 Core, B1 Filtration Chamber No. 1: Underneath the wreckage, underwater.
• Shell 2 Core, Locker Room (Where Emma Emmerich is hiding): It's hiding inside the locker (This locker can only be opened in Extreme mode. However, there's a Claymore mine that is set inside the locker, which will kill the player instantly if it's not destroyed or picked up).
• Strut E: In the room with the Digital Camera, behind the northernmost boxes.

Solid Snake can grow his facial hair after being shaved. If the player picks up the Shaver in Strut A of the Big Shell near the Deep Sea Dock, and give it to Snake when they first meet on Strut B, he will be clean shaven when they see each other again after escaping the Torture Room. However, if the player waits a week his facial hair will grow back.

In a 2004 interview with GameCenter CX, Hideo Kojima revealed a pair of jokes that were dropped from the final game:

According to Hideo Kojima & Yoji Shinkawa in the documentary on the making of Metal Gear Solid 2 from the game's bonus disc, Shinkawa stated that Rosemary represents Kojima's ideal, classy and intellectual woman. Some of Raiden & Rosemary's conversation were influenced by Kojima's own life experience.
Kojima stated that the idea for April 30th stemmed from his relationship with his wife, where she kept reminding him about that date before they were married. One evening, he had a date with his wife, but he completely forgotten about it, which caused him a lot of crisis in their relationship.

In order to hide the twist of Spoiler:Snake being a decoy protagonist and Raiden being the true main character, director Hideo Kojima personally put together the game's trailers himself. The footage for the E3 2000 trailer was recorded from Spoiler:the Tanker segment at the start of the game, when Snake is the playable character, and in the E3 2001 trailer, Spoiler:several scenes that focus on Raiden in the actual game were edited to swap him out with Snake.

Solidus Snake's swords are named "Minshuto" and "Kyowato". This translates to "Democrat" and "Republican", respectively.

After defeating Solidus Snake at the end of the game, he falls to his death from the Federal Hall building. Just before he falls however, if you look closely, you can see his lips move slightly in the brief moments that they are not covered by the collar of his exoskeleton. By replacing Solidus' model with Solid Snake's (who shares most of his facial features) through mods, it reveals that Solidus was actually saying one last message to Raiden. However, the dialogue during this moment is still muted, so his last words remain unknown.