Boy! I'm no expert. Wish I was. All I have is experience with both yorkies and chihuahuas. This is just my opinion, so please no one take offense. I just cannot agree that growling is a normal or good thing except when they might be playing with some of their toys. I have never had a little dog do this in over 40 years of having little dogs. If it was me, I would wonder if this little one is feeling threatened or intimidated for some reason or has not been adequately socialized. These are just things I would consider. Sometimes these behaviors may go back to the breeders. It's hard to say.
Speaking about temper tantrums, we used to have a cute little chihuahua and every time we told her no when she was a puppy, she would grab her pee pad and run through the hall. You couldn't see her, just the pad flying through the halls.
