This article lists the secrets in Metal Gear Solid: Peace Walker.
In the Mount Irazu facility's parking garage, there are eight parked cargo trucks. The license plate numbers for each of the trucks are as follows:
- Truck closest to the entrance: SHINA GAWA 57577 PEACE SENTINEL (contains rows of fish).
- Truck second closest to the entrance: CENTRO AMERICA 48273 PEACE SENTINEL (containing several "metal gears"; a confused Snake will say "Metal... Gear?!").
- Truck third closest to the entrance: CENTRO AMERICA 63824 PEACE SENTINEL (contains Hideo Kojima, as he was born on August 24, 1963; Snake will say "Director!" ("Mr. Kojima!" in the English version), with a fulton sound effect being heard shortly thereafter with the implication that Kojima was fultoned out to Mother Base.
- Truck fourth closest to the entrance: CENTRO AMERICA 64779 PEACE SENTINEL (technically empty, but it was the one that contains the nukes).
- Truck fourth farthest from the entrance: CENTRO AMERICA 00000 PEACE SENTINEL (contains several Master Otenko plushes, Solar Boy Django's sunflower-like companion from the Boktai series; Snake will yell "SUNLIGHT!").
- Truck third farthest from the entrance: CENTRO AMERICA 777 PEACE SENTINEL (contains poker chips and gold coins).
- Truck second farthest from the entrance: CENTRO AMERICA 140.96 PEACE SENTINEL (contains some briefcases and a poster of Mei Ling; the truck's plate is her original Codec frequency).
- Truck farthest from the entrance: CENTRO AMERICA 66447799 PEACE SENTINEL (contains crates).
- Truck fourth closest to the entrance: CENTRO AMERICA БЕИ PEACE SENTINEL (this is the truck that Vladimir Zadornov was hiding in when he escaped for the fifth time. It also replaces the truck with 64779 as the License Plate number).
Metal Gear Mk. II makes an appearance in the cutscene between Snake and Huey Emmerich after the Pupa battle. Also, pressing the R button at a certain point (specifically, when Big Boss says "So that's who that guy was...") in the same cutscene will show an image of Hot Coldman doing his V-for-Victory sign shortly after shoving Huey down the stairs.
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.
In the cutscenes where Paz Ortega Andrade is introduced, after Big Boss rescues Amanda Valenciano Libre from Chrysalis near Bananal Fruta de Oro, the introduction of Cécile Cosima Caminades, and the introduction of Strangelove, zooming in on the characters will reveal some things: Zooming in on Paz will have her red cloak come off to reveal her school uniform, and further zooms will show her in her underwear; zooming in on Amanda will show the extent of her fractured bones in her legs; zooming in on Cécile will have a popping sound being heard; zooming in on Strangelove will reveal that her "heart" is full of lilies.
In the cutscene where Big Boss is captured, the player can complete the quick time event, which cumulates in Snake stealing a card key from Strangelove before being arrested.
Aldea de los Despiertos search
Although the primary mission objective is to locate Chico (or in the case of Chapter 5, Zadornov), 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. The right door will have Big Boss reacting to the discovery (Chico has him inquiring if the prisoner is Chico, while Zadornov has him exclaiming "Gotcha!").
In a briefing file with Cécile, Kazuhira Miller will talk about how her name sounds similar to "Kojima Kaminandesu." In Japanese, Kaminandesu can be translated into "is God", therefore translating the phrase as "Kojima is God." She's named after a real person, Cécile Caminades, the former Communications Manager of Konami France.
Date with Paz
In Extra Ops, there is a mission where the player can date Paz. During that mission, if the player has the Love Box, they can invite her into the box (actually, using a cardboard box of any sort is required for completing the mission). If the player does the mission while wearing the naked uniform, Paz will become embarrassed and will run away from them. If the player beats this mission with an "S" rank, the next time they do the mission, Paz will be in her underwear. Similarly, there is also an Extra Ops mission where Big Boss dates Miller, and has similar methods to completing the mission as well as similar results with an "S" rank.
If the player uses the Codec near a river, they will contact Huey who mentions a strange dread of water. This is a reference of his eventual suicide by drowning.
Unlocking Extra Ops 63, 64 and 65 will allow the player to play the game Pooyan. The player will have to shoot all the fultoned soldiers that appear. Pooyan is a well known Konami game. In a briefing file, Miller tells Snake that his neighbor had a pig named Pooyan.
The logo for Peace Walker (peace sign with airplane) looks similar to one of the palletes in Metal Gear Solid 3's title screen.
When the player shoots a soldier with the Tanegashima, a tornado will shoot up the soldier into the air and Miller will call them and say "There's a soldier hanging on the helicopter", along with other quotes.
After unlocking the Extra Op 121, the player can go to an island where they can fight three monsters from Monster Hunter . Players can fight the Rathalos, Tigrex and Gear REX. The Rathalos and Tigrex are from Monster Hunter Freedom 2. Gear REX was actually created by the Metal Gear developers and isn't featured in any Monster Hunter game.
Mother Base staff
Series creator Hideo Kojima makes a cameo in this game as a recruitable soldier for the Militaires Sans Frontières. He can be recruited by selecting the truck in the Crater Base garage with the license plate "CENTRO AMERICA 63824 PEACE SENTINEL." In addition, due to the nature in which he is recruited, he is the only normal soldier who can be fired and then rehired by repeating the recruitment process. In fact, the plate numbers indicate Kojima's birth date: 24th August 1963 (yy/mm/dd). His profile says "70% of my existence is made up of movies, the other 30% is up to you", a take on a famous quote from Kojima. Besides Kojima, the player can also obtain soldiers that has the faces of: Yumi Kikuchi, Akio Ōtsuka, and Sugita Tomokazu who were the voice actors for Dr. Strangelove, Snake, and Kazuhira Miller, respectively.
Looking at soldiers' profiles contain many hidden jokes. One of the soldier says "I have a friend named Johnny, do you know him?", referring to Johnny Sasaki's grandfather. Another says "If I have a girlfriend one day, I would like to go in a cardboard box with her." Another one runs to Snake, in disbelief that another soldier believes Santa Claus isn't real. Yet another reference is to a song, a soldier says "Balls to the wall, boys". Another soldier says, "When this battle’s over, I’m gonna go home and be a shrimper. Me and my buddies are gonna pitch in an buy a big boat."
Various characters from past Metal Gear games make cameo appearances as the randomly-assigned profile pictures of recruited personnel. Various fans have pointed out the following examples, though some portraits' similarities may be unintentional: Laughing Octopus; Raging Raven; Crying Wolf; Screaming Mantis; Vamp; Fatman; Fortune; Emma Emmerich; Peter Stillman; The Sorrow; The Fear; Ed; Jonathan; Johnny Sasaki; Mei Ling; Naomi Hunter; and Rosemary. Various staff members, besides Kojima, were used as well. Some faces also resemble ones used in Metal Gear Online, while others are reminiscent of characters from other Kojima projects, such as, Snatcher, Policenauts, and IdeaSpy 2.5. Some of the portraits were also reused from the portraits used in the cutscene where Naomi explains the Sons of the Patriots system in Metal Gear Solid 4.