Explanation:
Castform is unique in the Pokémon universe for its ability to change forms based on current weather conditions. This feature allows Castform to adapt its type to either Water, Fire, or Ice, corresponding to rainy, sunny, or snowy weather, respectively. This adaptability makes Castform a versatile combatant in battles influenced by weather effects. Its signature move, "Weather Ball," also changes type based on the weather, making it more effective in various battle scenarios. Castform's design and abilities reflect its role as a weather Pokémon, highlighting the creative interplay between Pokémon characteristics and environmental factors in the game.