Pokémon Mystery Dungeon Team GoGetters out of the Gate (2006)

Charmanders voice calls out from the darkness if Squirtle is okay The sleeping boy wakes up and cant believe himself when he sees a talking Charmander Charmander then points out that hes a Pokémon too The boy takes a look at his reflection at a river besides him and sees that it is true He has turned into a Squirtle and has no recollection at all how this had happened