I recently reset my Macbook Pro with the operating system OS X Yosemite, and it seems that overworld NPCs and pokemon, characters, and other things like diggable patches all have a black texture.
However, when it's evening/night, and you walk under a street light, you can see the texture of the overworld sprite as it should be - not black.
CCleaner doesn't do the trick. Redownloading doesn't fix it either.
A friend of mine uses OS X Yosemite too, same issue.