From Bulbapedia, the community-driven Pokémon encyclopedia.
Cero Island (Japanese: セロアイランド Cero Island) is an anime-exclusive location. Located in the distant seas, it was featured in Getting More Than You Battled For!.
Ash and Goh visited Cero Island in search of Mew and traveled there by boat. While exploring the jungle, they encountered a group of Mankey, and Goh caught one of them. This enraged the other Mankey, leading them to chase Ash and Goh into a marsh where Ash nearly sank, only to be saved by Goh's Heracross.
Using Caterpie's String Shot, Ash and Goh started to climb over the Marsh, only to be ambushed by a Kingler and Krabby. Goh managed to catch Krabby as they continued along their journey. As Ash and Goh started to cross a river by jumping on the stones, a Gyarados attacked them but Goh was unable to catch it. After falling into the river, Ash and Goh ended up going over a waterfall.
After coming round, Ash and Goh encountered a group of Pokémon before meeting their protective guardian, Mewtwo. Ash and Goh attempted to battle Mewtwo with Pikachu, Lucario, and Cinderace but they weren't able to do any damage. Eventually Mewtwo decided to leave the Island and remain in hiding along with the Pokémon it had rescued from people, before teleporting Ash and Goh back to Cerise Laboratory.
Cero Island is uninhabited by people. Its steep cliffs make it impassable to most, while its dense jungles and rivers are home to many wild Pokémon.
Pokémon seen on Cero Island
Previously resided on Cero Island
|| セロアイランド Cero Island
|| From cero (Spanish for zero)
|| Cero Island
|| Same as Japanese