Each Pixelmon NFT came to existence on chain in its unhatched state, only upon hatching its rarity, origin and species are revealed to the holder. Every owner of a Pixelmon NFT will have the choice of hatching their specific Pixelmon in order to reveal which one they own. To do this, holders will need to visit the Pixelmon website and sign a transaction to trigger the metadata reveal. This entire process is gasless. In the future, for staking and other rewards that are based on rarity, all eggs will be able to receive rewards and will correspond to a Common set rarity.
You may reach the hatching page HERE.