Natu is a Psychic and Flying type Pokémon. It may be a flying type, but it cannot fly due to it's wings not being fully grown. It is usually shown hopping instead. It will stare at a human if it encounters it. A pretty high, curious and intelligent voice would suit this Pokémon.

Xatu is the evolved form of Natu. It usually stays still and quiet, because it is viewing the past and future at the same time. It can see the future with its right eye, and the past with its left eye. A stern, monotone, intellegent voice would work for this Pokémon. Even when predicting a terrible future, it will still sound pretty monotone and serious. But it may end up making a bird like sound that's higher than the voice it normally speaks in. The bird calls will be scripted however.