Mew made a cameo appearance at the start of the movie, and did not take a major role until later. A Mewtwo was cloned from Mew's DNA, extracted from Mew's eyelash. Later, Mew started appearing around New Island while Mewtwo was testing his starter Pokémon clones. Mew followed Team Rocket into the main part of the island.
When Mewtwo's other new clones were born, Mew came with them, but disappeared momentarily. When Mew reappeared shortly later, it tried to reason with Mewtwo, which led to a battle between the two. Ash stopped their battle by throwing himself in the middle of their attacks, which turned him to stone. After Ash was revived by Pokémon tears, Mewtwo flew away with its clones and Mew went with them. At the end of the movie, Ash briefly saw Mew in the sky, though Brock and Misty didn't see anything. After the credits are over, a brief scene plays showing Mew flying towards the mountains.
In Mewtwo Returns, Mewtwo briefly saw Mew after being thrown into the Purity Spring, but this was just his imagination. It briefly reappeared in a montage in The Rise of Darkrai, which chronicled the preceding nine movies. Mew physically reappeared in Mewtwo Strikes Back—Evolution, a remake of Mewtwo Strikes Back, where it played the same role.
Personality and characteristics
Mew has a very playful and curious nature, and it prefers having fun over fighting. It didn't even seem to understand that Mewtwo was wanting to fight it until one of Mewtwo's attacks actually hit it. When battling, however, Mew was shown taking the fight very seriously as well. After the battle, Mew quickly took back its serious side and resumed its playful personality, proving the fact that it had been fighting only because it had to defend itself. In the Japanese version, Mew also wanted to defend original, uncloned Pokémon, believing them to be just as good, if not better, than the clones.
This Mew was distributed to players who insert a serial code that were given away at 7-Eleven stores in Japan via 7-SPOT. Players need to go to different 7-Eleven stores and collect two different virtual stamps using 7-SPOT to obtain a serial code. The serial codes were available from July 11 to 31, 2017 at 7 am to 7 pm, and can be redeemed from July 11 to August 7, 2017.