I have a Magby that I caught and every time I bring it out in battle, a star appears on it. What does that mean? It doesn’t happen for any other Pokemon I have.
Your Magby is shiny. Congratulations!
A shiny Pokémon is a rare (1/4096) colour variant version, and displays a little star when it’s sent out in battle. Other than that, there is no difference between a shiny Pokémon and its normal counterpart.
To confirm this, you can check your Magby’s status page, you should see a red star near its model.
Source : Link , Question Author : Ash , Answer Author : Community