It is not known to evolve into or from any other Pokémon.
Jirachi is a small, white, humanoid Pokémon. It has short, stubby legs and comparatively longer arms. There are flaps on the underside of its arms, which give the impression of long sleeves. On its belly is a curved seam, which conceals a third eye, known as its "true" eye. Additionally, it has a normal pair of circular eyes on its face, with small, blue triangular markings underneath. On its head is a large, yellow structure with three points extending outward: one from the top and one on either side. On each point is a teal tag, known as a "wish tag". A rounded extension hangs from either side of the yellow structure, framing Jirachi's face. Two yellow streamers flow from this Pokémon's back, resembling comet tails.
Jirachi hibernates for extensive periods, forming a protective crystalline shell as it sleeps. However, it is still capable of fighting while asleep if it is in danger. It awakens for seven days every thousand years, but can also waken if sung to by a voice of purity. During the short periods when it is awake, Jirachi is said to grant wishes. However, in the anime, Jirachi cannot create an object that is desired from a wish. Instead, it teleports the desired object to the person that made the wish. In the Pokémon Adventures manga, Jirachi's wishes are granted by writing on the three tags located on its head. Due to only having three tags, Jirachi can only grant three wishes. The anime further reveals that Jirachi's awakening is linked to the Millennium Comet and that its third eye has the ability to absorb the energy Jirachi needs for hibernation. Although it is extremely rare, Jirachi can be found in the mountains. Jirachi is the only known Pokémon capable of learning the move Doom Desire.
Jirachi debuted in a major role in Jirachi: Wish Maker. It was revealed to only awaken during the week of the Millennium Comet, where it would search for a partner to be its friend, with the honor in the movie going to Max. However, by the end of the movie, Jirachi went back to sleep, much to Max's sadness.
Jirachi made its main series debut in Searching for a Wish!. A young girl named Gemma had been in pursuit of Jirachi, since she wanted it to grant her wish to restore her valley to the vibrant land it once was. Jirachi was initially shy towards her, but in the end, it warmed up to her and granted her wish before falling asleep again.
As the Emerald chapter progressed, the Frontier Brains discovered that Battle Frontier's owner Scott had known about Professor Oak's research on Jirachi, and wanted to reserve one of Jirachi's three wish tags for himself. In A Cheeky Charizard Change-Up II, Guile Hideout captured Jirachi before any of the Frontier Brains were able to track it down. Guile then advanced to the top of the Battle Tower, and after finding out how to get Jirachi to listen to one's wish, used the first wish tag to summon a powerful sea monster that would submerge the Battle Frontier. Guile then discarded Jirachi, thinking that it was no longer of use. This gave Emerald the chance to make the wish that would de-petrify the five Pokédex Holders, as instructed by Gold. However, it didn't appear to work.
After Emerald re-evaluated his relationship with Pokémon in The Final Battle VI, Jirachi finally listened to his wish and de-petrified the five Pokédex Holders. This intrigued Guile, who took Jirachi back and commanded its Doom Desire in an attempt to eliminate the Pokédex Holders and use the final wish tag. However, Guile was eventually defeated, and the sea monster that he summoned was destroyed by a combination of the "ultimate attacks" that all the Pokédex Holders' starter Pokémon had learned. In Epilogue, Scott made the wish he had reserved: to attract at least a hundred thousand visitors to the Battle Frontier on its opening day. Emerald expressed his gratitude and bid farewell to Jirachi as it returned to its thousand-year slumber.
Jirachi appears as a rare Poké Ball Pokémon in its first appearance in the Super Smash Bros. series. The chance of it appearing is 1 in 493 (the amount of Pokémon in the Generation IVNational Pokédex). Like the other "secret" Pokémon, it drops rare items instead of just flying away. In Jirachi's case, the items are stickers.
A Wish Pokémon. It's said to awaken for seven days once every thousand years, with the ability to grant any wish asked of it. It is truly a Pokémon of which dreams are made. In combat it uses its wish power to attack. Its attack, Doom Desire, which causes light to rain down from the heavens to do tremendous damage, is especially powerful.
Since Jirachi is only awake for seven days every one thousand years, it's an even bigger sleeper than Snorlax! It can't just be sleeping the whole time, though. It's probably hard at work deep in the land of dreams, strengthening its ability to grant people's wishes. If it detects danger while asleep, it can fight without even waking up!
Pokémon Pinball: Ruby & Sapphire: While in the Ruins, one of the slot machine prizes is the chance to capture Jirachi. Jirachi will move around and must be hit three times in 30 seconds for the capture to be successful. There is only one chance per pinball game.
Despite being legitimately obtainable in earlier games, Shiny Jirachi were previously locked out of Generation VI's Wi-Fi features prior to an update; this makes Jirachi the only Pokémon to have undergone this kind of issue.
Jirachi's design and ability of granting wishes probably refer to the habit of "wishing upon a star", so that the wish will come true. Considering its humanoid appearance and ability to grant wishes, it is also possible that it was inspired by Arabic myths about the jinn. In some myths, imprisoned genies would grant wishes to the person who released them. The tags of paper on its head are a reference toward the paper strips (短冊, tanzaku) written on Tanabata.
Jirachi is derived from желать zhelatʹ (Russian for wish). It may also involve 幸 sachi (wish, happiness, or fortune).
In other languages
Possibly from желать zhelatʹ (Russian for wish). It may also involve 幸 sachi (wish, happiness, or fortune) or the anglicized jireh (yireh, Hebrew for provider)