I have two yorkies. One who is a ball fetching fool, the other could not care less about toys or balls. Couver LIVES for fetch. I have to cut him off so that he doesn't over exert himself when we play fetch. He also does not share, so we do not play fetch at the dog park because he gets possessive. He knows his sister doesn't want his ball, but he doesn't get that other dogs do not care about it, and he will bite any dog that gets near him during ball time. Luckily we know this is a trigger for him, so we just avoid it
Khloe on the other hand, has NO interest and very rarely can I get her excited enough to even put a toy in her mouth. It's like she thinks thinks she's above it.
It's so funny how different yorkie personalities are!