Mystery Food X is a substance featured in the Persona series, specifically in Persona 4. It refers to "food" cooked by the female members of the Investigation Team, used in several scenes for comedic value.
In all its incarnations, Mystery Food X is a kind of food that gives off a purple miasma. The taste is revolting and has been seen to cause momentary illness. It originally was used as a label for the curry meal that Yukiko and Chie prepared for Yosuke Hanamura and the P4 Protagonist. Later, the term has been used for any meal prepared by Yukiko Amagi, Chie Satonaka and Rise Kujikawa. Each of their meals have a particular aspect which classifies it as Mystery Food X: Chie's food is shown to be generally unpleasant, Yukiko's are either tasteless or odd due to her use of unusual ingredients, and Rise's are extremely spicy due to overuse of spices and hot peppers. The girls seem to be unaware of their poor cooking skills given that they never taste their own food nor do they ever eat their own finished dishes.
When the protagonist, Yosuke Hanamura, Yukiko and Chie go with the rest of the Yasogami High students on the school camping trip, Yukiko and Chie take it upon themselves to make curry for their end-of-day meal. The protagonist sees them by chance getting ingredients. When at camp, despite its unpleasant appearance, the two cooks feel unable to taste it themselves, so give it to the men. When Yosuke tastes it, he spits it out and momentarily keels over. After berating the girls, they insist that the protagonist try it. If their courage is not high enough, they will not be able to, but even pretending to eat it shows the protagonist how bad it is. This leaves them as the only group of students without food.
A similar experience is felt in August after the party defeat Mitsuo Kubo: as part of the celebrations for apparently solving the case, the protagonist, Yukiko, Chie and Rise prepare food, which they have at the Dojima residence with Nanako. In the end, the protagonist's food is the only one that doesn't either taste wrong or outright bad. The men also fear another repeat of events at the Chrismas party to celebrate Nanako's recovery after being kidnapped and forced into the Midnight Channel. This time, Naoto Shirogane is also helping, and the cake ends up being very good, though Naoto comments that it was their third attempt. Later, Yosuke would say Naoto's involvement was why the cake came out to be nice at all.
During the bonus Valentine's Day event, Nanako decides to make chocolate for the protagonist and enlists the help of the Investigation team girls for advice on how to make it. As a result of their suggestions (Naoto simply saying that the protaginist would like anything she made him), Nanako ends up making a Slime shaped "chocolate", causing the protagonist to be very alarmed. Although he nearly backs out of eating it, Nanako's innocent comment declaring that she loves him forces him to eat it to keep her happy. Unfortunately, the "chocolate" causes him to black out.
Events proceed very much as they did in the game for the Camping Trip, with the added element that Hanako Ohtani appears and finds the curry delicious, which greatly puzzles all of them.
Persona 4 ArenaEdit
Mystery Food X makes a minor appearance as a trophy. To get it, the player must spam Teddie's crouch or jump button until he throws some curry onto the field, then pick it up before the enemy. Doing so will earn the trophy, but also poison Teddie.
Persona Q: Shadow of the LabyrinthEdit
During the Persona 3 side of events, during their exploration of the Evil Spirit Club, Yukiko offers some cookies to Zen and Rei. Rei has them and initially seems fine, but when Zen has them, he freezes in shock and seems to faint on his feet. Rei then faints. When she comes to, she says she dreamt she was being held down and sand poured into her mouth. This provokes the P4 protagonist and Yosuke to wonder how much more Mystery Food X will "evolve". Mitsuru Kirijo expresses an interest in Yukiko's cookies, finding military value in its hallucinogenic effects.
In the Persona 4 side, when the group enter the final Culture Festival labyrinth, the group are confronted by the Macho Man F.O.E, forcing the group to flee. While the men take one route and Kanji is captured by the F.O.E, the women go another way, finding temporary safety. If the protagonist goes with them, they see in full detail what happens. As the F.O.E approaches, Naoto has the idea of using the girls' food to create a powerful weapon against the F.O.E. They use the contents of a lunchbox prepared by Yukiko, a muffin baked by Chie, cookies made by Rise that she gave to Chie, and rice balls prepared by Fuuka which were being carried by Aigis. Either at the protagonist's suggestion or on her own, Naoto decides to mix them all up, creating what she dubs "Mystery Food X: The Final Edition", a concoction so potent that it stings Rei's eyes and causes Zen to refer to it as "a chemical weapon". When the F.O.E appears with Kanji, Zen fires arrows dipped in the substance at it. The first shot accidentally catches and incapacitates Kanji, but the second strikes the F.O.E and kills it outright. Mitsuru is so impressed that she voices her desire to take it for examination and replication at the Kirijo Group's R&D labs, much to the other women's chagrin, and Naoto followed by saying such attack was the only choice available that time, and cannot be reproduced again.
Persona 4: Dancing All NightEdit
Mystery Food X is brought up at the end of the story when Kanami makes the Investigation Team a boxed lunch as thanks for rescuing her and solving the case of the game. Most of the guys fear that Kanami's food will be like the other girls, but to their surprise, her food is delicious.
During the bonus prologue, Yukiko mentions during her interview that she has continued to practice how to cook. When Minoru Inoue expresses a desire to try her cooking someday as a visitor at the Amagi Inn, the boys quickly try their best to deter him, stating amongst themselves that they will not allow anyone else be a victim to the girls cooking like they were to their curry. Later, the Investigation Team and Inoue is invited to the Dojima Residence and the girls quickly offer to help cook the meal. While Inoue is excited to get a sample of "Amagi cooking", the boys are less than excited to hear that they will help.