Mew is the rare #151 Pokémon in the Pokédex. Like in the main games, Mew is incredibly hard to get, but unlike the main games, you can get it here without the use of an event. The method to get Mew requires a lot of skill to obtain and requires a lot of time in one session without ending the game.. The steps you have to take are as follows

1. Defeat all the bonus stages of the table you're on twice each
2. Make it to the Indigo Plateau area

Once you have made it to Indigo Plateau, Mew will have a small chance of appearing, approximately 2%. Keep at getting it in the area and eventually, it will appear and require the activation as all Pokémon.

Once Mew appears, when you hit it, you may find that the word "CATCH!" isn't lighting up. This is because you can't technically capture it. All you can do is keep hitting it until time runs out. With every hit, you will get 3,000,000 points so just keep hitting it and get as much as possible. Once the time runs out, Mew will be added to the Pokédex.