During the mission "Infiltrate the Crater Base", if the players choose certain truck Metal Gear Solid creator and director Hideo Kojima could be unlocked as a character to use for their team at Mother Base. Kojima has an S-rank at both Medic and Intel.
Metal Gear Solid: Peace Walker did not start as a Hideo Kojima game. Originally, Kojima intended to lay out the overall concepts and guidelines, then let the rest of the development team take the reins. But when the themes of Peace Walker started coming together, such as nuclear deterrence and the Cold War, Kojima worried it may be too confusing and alienating for a younger audience, which was the target demographic. As a result, Kojima became more involved, serving as the director, producer, and writer, in an effort to keep the narrative as clear as possible.
The color yellow and butterflies are prominent themes in the game because Konami wanted to have more of a pop-feel in Peace Walker that would appeal to the younger school aged kids, which were the target demographic.
Konami and Capcom collaborated together during the development of Metal Gear Solid: Peace Walker. In the game, players can unlock special missions where they face-off with bosses from Capcom's Monster Hunter franchise, including one named Gear Rex, also known as Nuclear Dragon.
Hideo Kojima revealed in an interview that Metal Gear Solid: Peace Walker had a major inspiration. At the time, Kojima's son was fascinated with Pokemon: Gold and Silver and Kojima didn't understand why until he started to play them. He loved playing them so much, that he ended up playing through them twice and became addicted. In Pokemon: Gold and Silver, after you play through the main area of the game, Joto, you gain access to a redone version of Canto, from Pokemon: Red and Blue, the two preceding games. Metal Gear Solid: Peace Walker also features vital story sequences after the credits for players who fulfilled specific requirements. At the time of Peace Walker's release, it was the most involved post-credit content for a Metal Gear game and it was inspired by Kojima's experience with Pokemon.
At the mining facility, before fighting Cocoon, you can climb one of the roofs of one of the buildings and find a haystack at the bottom. If you jump off of the building and into the haystack, you will perform a leap of faith from the Assassin's Creed series. Miller will then tell Snake about stealthy assassins using the haystack to hide from enemies.
In an interview with Famitsu, Hideo Kojima stated that Metal Gear Solid: Peace Walker wasn't as visually impressive as his past games, but that wasn't the point. Kojima said you had to play Peace Walker in order to get it; referring to the various new systems and how they play off one another.
A recurring theme in the Metal Gear series is to show the danger of pursuing something at the cost of everything else. This is present in the game, as Dr. Strangelove is shown to idolize The Boss so much, that she agrees to develop the mammal pod in an attempt to resurrect The Boss, even though it will directly lead to a nuclear attack.
In Japan, Metal Gear Solid: Peace Walker sold over 570,000 copies during it's first two weeks. Despite internal hopes that the game would be an international hit, sales were very poor outside of Japan, failing to chart in most countries. According to Hideo Kojima, weak sales of Peace Walker, are what caused Kazuhiro Miller to be removed from the covers of the international versions of Metal Gear Solid V: Ground Zeroes.
In one of the missions where Snake must locate Chico, the player can identify various aspects in the doors. One will be empty if peeked in, with Big Boss mentioning that there's no one inside. Another will have an old man snoring and chuckling in his sleep, with Big Boss reacting with suspicion. One will have running water with a prisoner sobbing for his mother. Yet another one will have Big Boss witnessing someone going to the bathroom and nearly blowing his cover.
During cutscene 11 "The Man in the Crater Base", a Gekko from Metal Gear Solid 4: Guns of the Patriots can be spotted on the left side of the screen during Huey's explanation. Zooming in on the bottom right corner will reveal Metal Gear REX.
Japanese beverage firm, Suntory, released a special line of eight cans in Japan that have images of various Peace Walker characters for the Mountain Dew and Pepsi Nex lines. The drinks are promoted in the game as health items, with Snake possibly getting a Mountain Dew shirt after the player inputs a special code found in the actual cans. Japanese apparel brand Uniqlo also ran a similar promotion. However, the labelled products were only available in the Japanese version; their counterpart in the North American and European version would have generic names and the MSF logo.
In the game, the player can use various incarnations of Sony Walkmans to listen to the game's background music. Sony also released a limited-edition W Series Walkman, the NWZ-W252CAMO, which comes with special game codes, six exclusive tracks from the game, and a special camouflage skin.
Peace Walker was remastered for the Xbox 360 and PlayStation 3 as part the Metal Gear Solid HD Collection. This remaster features HD visuals, 60fps framerate, touched up textures, and improved controls. Although this HD collection was also released on the PS Vita, Peace Walker was not included. Series creator Hideo Kojima explained that the original PSP version was backwards compatible with the Vita, and the Vita did a great job upscaling the visuals along with being able to override code to improve controls. e.g. Allow the Vita's second joystick to control the camera whereas the PSP had the face buttons control the camera.
Before Peace Walker, Metal Gear games were largely about traveling along a linear path toward a single objective preferably through the use of stealth. Although that's also true in Peace Walker, players have much more freedom with their type of play style and smaller decisions, made when controlling Mother Base, could impact something else quite differently.
The first time in a Metal Gear game where the player has freedom of choice in the boss battles. This is due to having specific parts from the mechs intact after you defeat them, as it will allow players to have access to the later parts of the story due the mech parts being used to develop your own Metal Gear, Zeke.
The first Metal Gear game that offers robust multiplayer features. Players can participate in matches, such as two players being able to play cooperatively throughout the main story missions, four players being able to participate in numerous boss battles, and six players being able to compete in Versus ops.
In some of the trucks in the 'Infiltrate the Crater Base' mission, players can find funny things such as a poster of Mei Ling, from Metal Gear Solid 1,2, and 4, as well as gear made of metal, which causes Snake to say "Metal... Gear...". Also, one of the trucks contains several Master Otenko plushes, Solar Boy Django's sunflower-like companion, from the Boktai series. This causes Snake to yell "Sunlight!".
The trivia item below may give away important plot points.
The first Metal Gear game where the main character is not responsible for the death of the main antagonist. In the game, Hot Coldman, the main antagonist, dies in the game due to the amount of blood loss after being shot by Vladimir Zadornov.