From Bulbapedia, the community-driven Pokémon encyclopedia.
A Pokémon's cry is the sound it makes. In most of the franchise's interpretations, this is only its name and various phrases derived from its name. However, there are several instances of talking Pokémon.
In the games
When a Pokémon is released from its Poké Ball, it will call out its cry. It will also cry out when using certain moves, such as Growl and Hyper Voice. If the Pokémon faints or comes into battle when injured during Generation III and Generation IV, the cry will sound, but it will be altered slightly. Pokémon with evolutionary relations to each other (such as Charmander and Charmeleon) will have notably similar cries.
In the wild, cries of the Pokémon found in the player's current location can occasionally be heard in the Generation III Hoenn- and Kanto-based games. Also, if the player's first Pokémon in his or her party has the ability Swarm, then these cries will be more common than before.
In the anime
Most Pokémon will only say their names, and will communicate using those syllables. For example, Ash's Pikachu has been known to use the three syllables in the word "Pikachu" in various combinations to refer to several characters, including Ash (Pikapi), Misty (PiKachupi), Brock (PikaChu), Togepi (Pipipi), Team Rocket (Pipikachu), and "My name is Pikachu" (PikaPikachu).
Due to Pokémon being dubbed, sometimes, the original cry of a Pokémon is preserved in the anime, more often than not if the name is either similar or the same in Japanese and English. An example of this would be Charizard, which can, if listened to closely enough, be heard to cry out Lizardon instead. Likewise, all Onix can be heard to cry out Iwark.
Some Pokémon, such as Victreebel, Porygon, Starmie and Staryu, cries are unrelated to their names at all. For example, Victreebel makes a screeching sound while Staryu has a cry that sounds like "hai-yah!!!".
- A Few pairs of Generation I Pokémon share the same cry, despite not being related by evolution.
- According to a Pokémon Sunday clip, Shaymin's Sky Forme and Land Forme are revealed to have different cries, making Shaymin the first Pokémon to have different cries for different forms.
- From Generation II onwards, possibly due to improved technology, very few Pokémon were released with cries similar to another; those that do have similar cries are usually related by evolution as they were in Generation I. As the generations continue to pass, the calls of new Pokémon seem much cleaner and more refined, while the cries of Pokémon released in previous generations, in comparison, sound more like the electronic beeps they are. In particular, the cries of new Pokémon in Generation IV are mostly recognizable digitized sounds, such as birds chirping for Starly or a xylophone being played for Kricketot.
- Despite there being 151 Pokémon in Generation I, there are only 37 completely different cries in the game. However, different Pokémon's cries are either pitched up, down, faster, slower, or disable one of the sound channels, making it harder to recognize. For example, Charmander and Charmeleon's cries are the same, but an instruction in the game tells the pitch for Charmeleon to be lower than Charmander's. Despite this, some Pokémon share the exact same cry with no sound tweaking, such as Charizard and Rhyhorn. In Generation II, there were 30 new cries introduced, applying to the same rules as before.
- One of the cries of a glitched Pokémon in the first generation games sounds very similar to Crobat's cry. This shows that Game Freak may have already been considering an evolution of Golbat.