There is a very rare chance that a Pokémon in the wild will come to the player's Pokémon camp while they are playing in it and ask to join the player's team. If the player selects the "Yes" option then not only will the Pokémon be able to join the camp but the Player will have also "caught" the Pokémon without battling it (it will go into one of the Player's Poke balls).
Contributed by PirateGoofy