Well, poorly bred Yorkies (the one they use for petshops) now look very much like bow-legged Silkies. I wouldn't be surprised if that was, indeed, a Yorkie/Chihuahua. Besides, petshop breeders usually breed with a kennel full of in-heat "purebred" (if you can call it that) females and throw a male dog of a different breed in that kennel. The male does his work, you know what breed the puppies will be, and the breeder gets his/her filthy, filthy money.