I've heard somewhere that regardless a dog's size it's super important to remain the pack's leader, the alpha dog. Even if it's a Chi or Yorkie. Is it true? I can't imagine how my being the alpha dog can influence a Yorkie? They're so small and adorable, these little cuties! ^_^
It's very true. Even the smallest of dogs can end up ruling you if you don't take and show your lead role as the alpha dog of the household.

The smallest dog we ever had was a 2 pound teacup chihuahua. His name was Chiko, and he ran our house. No one could do anything with him other than my mother. He was the most viscious dog EVER! We ended up having to find him a new home to live in.

It's true and it's vital for your and your dog if you both want to live a happy life. As you can see from JustaBrat's post, even a small dog will try to rule the household if you let it to. The size doesn't matter because even toy breeds have dog instincts and spirit. Unfortunately, many people treat Yorks and Chihuahuas like alive toys, literally. They spoil them, they dress them, they take them everywhere in bags, they forgive any unacceptable behaviour, etc etc etc. They don't even realize that even a small dog needs sufficient physical exercise and daily walks! I don't mean that showing love and affection to your little companion is bad, I mean that even a little companion is a dog, an animal first of all, and it has its own doggy needs, including the need of a leader. If there's no leader, the dog will try to become one.