From Bulbapedia, the community-driven Pokémon encyclopedia.
In the Pokémon world, a great deal of advanced technology is shown to be used by humans. Among this technology is the ability to create artificial Pokémon—Pokémon that have not emerged naturally but have been created, either through experiments or indirect means.
These Pokémon, other than being artificially created, are no different from natural Pokémon. They can breed, evolve, be found in the wild, be captured and be trained just as ordinary Pokémon would. Even these Pokémon have DNA which draws from the genetic code of Mew, the supposed ancestor of all other Pokémon besides these.
Known artificial Pokémon
#088 Grimer and #089 Muk
Human pollution indirectly caused Grimer's creation.
Grimer, and consequently Muk, were created from human pollution in a stream exposed to X-rays from the Moon, according to several Pokédex entries. As they were created from genetic waste, Grimer and Muk are Poison-type Pokémon.
#100 Voltorb and #101 Electrode
Voltorb takes on the appearance of a Poké Ball.
Voltorb and, as such, Electrode, first appeared, according to several Pokédex entries, at the company where modern Poké Balls were developed. It is rumored that it was first created when a Poké Ball was exposed to a powerful pulse of energy.
#137 Porygon, #233 Porygon2, and #474 Porygon-Z
Porygon can exist as computer data in cyberspace.
Until the re-discovery of Golett, Porygon was thought to be the first Pokémon created deliberately. It is the first Pokémon deliberately created using modern technology, as the result of an experiment by the Pokémon Lab in Kanto. Silph Co. possesses a report on the Pokémon, calling it the first "virtual-reality Pokémon." Because it is made up entirely of computer data, it is able to exist in cyberspace. According to some Pokédex entries, there is copy-protection data embedded in the program to prevent illegal reproduction. Porygon was developed to work in space, but it lacks this ability until evolving.
Porygon possesses two evolutions, both possible through artificial upgrades. Porygon2 evolves from Porygon when it is traded while holding an Up-Grade. According to some Pokédex entries, it is designed to work in and explore space; despite this, it is unable to reach and explore other planets. Unlike its predecessor, Porygon2 is not limited to what is contained in its program—it is capable of learning.
Porygon2 evolves into Porygon-Z when traded holding a Dubious Disc. It is a modification of Porygon2, designed for travel between different dimensions. However, it did not work as planned so it exhibits erratic behavior and is capable of displaying emotion.
Mewtwo was created artificially as a clone of Mew.
Mewtwo is a powerful Legendary Pokémon, the result of gene splicing experiments using the DNA of Mew. According to logs found in the Pokémon Mansion in Kanto, Mew "gave birth" to Mewtwo after an embryo had been developed. This is inconsistent with Pokémon traditionally being born from Eggs. It has a somewhat artificial appearance, most notably the tube protruding from the back of its neck. Like Mew, it harnesses powerful psychic energy. However, Mewtwo's power was amplified to exceed Mew's power in an effort to create the most powerful Pokémon ever created.
#343 Baltoy and #344 Claydol
Many Pokédex entries of Claydol state that it and its pre-evolution, Baltoy, were originally clay figures created by ancient people. The figures came to life after being exposed to mystical rays.
Castform was created by scientists and can change forms with the weather.
Castform was created by scientists at the Weather Institute in Hoenn to help predict the weather. Because of this, it has the ability to change its form and type with the weather condition.
Banette is a plush doll that was thrown away. It seeks the child who abandoned it.
#568 Trubbish and #569 Garbodor
Trubbish's Pokédex entries says it was created when garbage and industrial waste mixed, causing a reaction that generated Trubbish. Garbodor, as its evolution, springs from the same source.
#622 Golett and #623 Golurk
Golett and Golurk were apparently created by an ancient civilization to protect people and Pokémon alike.
Other Pokémon influenced by humans
Some Pokémon that formed naturally are shown to be altered in some way by human involvement.
Deoxys is said to be a virus which fell from space while attached to a meteor. Once on Earth, this virus was mutated by accidental exposure to a laser beam which transformed it into a Pokémon. Its DNA remains unstable and it will mutate further when exposed to certain sources of extraterrestrial radiation.
#412 Burmy and #413 Wormadam
Wormadam donning the Trash Cloak
Burmy create outer cloaks out of their habitat. This may be composed of natural materials, as seen in its Plant Cloak or Sandy Cloak, or of artificial insulation as seen in its Trash Cloak. Burmy's cloak will change depending on the location of its last battle.
Female Burmy evolve into Wormadam, which retain the last cloak it had as a Burmy, including the Trash Cloak.
Spiritomb were once 108 separate entities whose sins caused their spirits to be bound together into the Odd Keystone as this Pokémon. The Keystones were then separated from the Hallowed Tower, which triggers Spiritomb's release.
Rotom has the ability to take over man-made appliances, such as this lawnmower.
Rotom has the ability to possess toasters, washing machines, refrigerators, electric fans, or lawnmowers.
Genesect, a Legendary Pokémon, was a different Pokémon many years ago. However, in Unova, Team Plasma reconstructed it from a Fossil with the goal to create the most powerful Pokémon ever. N cancelled the project due to his belief that a Pokémon modified by science would lose its pureness. One scientist, however, kept working on the project in secrecy, disagreeing with N's decision to cancel it. The scientist equipped Genesect with a metallic body, a cannon behind its head, and items known as drives which change the type of its signature move, Techno Blast.