Brock's Croagunk

Brock's Croagunk was first seen in the episode Gymbaliar! It was waiting outside of a shop until it saw Meowth walk out and then it followed him. Jessie then used the Croagunk in her fake Gym. Team Rocket ended up blasting off and Croagunk was left behind. Brock asked him if it wanted to come with him and it said yes so Brock caught it.