Mew is a small, cat-like Pokémon with small, pointed ears, blue eyes, a long, thin tail with a large bulge at the end, and large feet with three toes. It is covered with a layer of fine, pink hair, only visible with the aid of a microscope. It has extremely short arms with three fingers on each paw, and has small, orange paw pads on the undersides of its feet.
It is said that Mew's DNA possesses the genetic composition of every existing Pokémon species, thus allowing it to use all known Pokémon moves. Its possession of every Pokémon's DNA also allows it to devolve Pokémon, as show in the TCG through its moves Devolution Beam and Devo Crush.
Mew was the very first Pokémon trademark ever to be applied for and registered, which is the reason why it was made "the ancestor of all Pokémon."
Mew is said to hold the DNA of all Pokémon. This is supported by the fact that it is one of only three Pokémon able to learn Transform, the other one through leveling being Ditto (Smeargle may as well by using its own move Sketch ). This also supports the fact that Mew is the ancestor of all Pokémon.
Mew and Ditto have similar normal and shiny colours.
Despite Mew's DNA being used to create Mewtwo, Mew comes after Mewtwo in the Pokédex.
Despite being labelled "the ancestor of all Pokémon" it is unknown if Mew was actually the first Pokémon, it was the first that was trademarked but story wise Arceus is said to have been alone when it was born and Arceus created other Pokémon, it is therefore unknown if Mew was born first and created Arceus or Arceus created Mew to hold the DNA of all Pokémon that Arceus created from then on.
Although it can learn all moves, Mew can't learn powerful and rare moves such as Blast Burn, Judgment, and Freeze Shock, mainly because some moves are to be learned by a specific Pokémon, and Mew cannot learn them under a specific condition.
It is the only known Pokémon to have its DNA used in a cloning process to create a different Pokémon: Mewtwo was created by cloning and gene splicing, Team Rocket (who were behind the experiments) were planning on creating a Mewthree. However, this plan failed when Mewtwo destroyed the lab.
In Japan, a pink Nintendo DS was released with Mew on it.
In Pokémon Red, Blue, Green, and Yellow, it was only officially available through events running during 1999-2000 outside Japan where the events ran approximately 4 years before. Today it's impossible to complete the PokéDex for these games without doing the Mew Glitch or using a memory modification device like the Gameshark, Action Replay, or Xploder.
Mew was the first event Pokémon introduced.
Mew wasn't originally going to be an actual Pokémon; it was originally just a prank set up by the developers, and behind the creators' backs, no less. However, due to all the publicity it got, it became official.
In celebration of Pokémon's 20th anniversary, a Mew could be obtained via mystery gift at select GameStop stores on February 1 - February 24 for Pokémon X/Y or Omega Ruby/Alpha Sapphire. In Australia, EB Games is still giving out Mew codes.
Mew placed 3rd in a special poll created to see which Pokémon was the most popular to be distributed for the upcoming movie Volcanion and the Ingenious Magearna..