My mother used to breed Yorkies. One litter of 5 puppies had 4 that grew to be about 5 lbs as adults. However, the 5th puppy turned out to be a whopper and grew to be 25 lbs. He was returned to her because the owners didn't want him anymore
She had a lifetime guarantee policy where an owner can get their money back if they ever wanted to give the dog back. I don't know why they didn't want him because he was really sweet.
She has a picture of him somewhere. She's a lurker on here but maybe she will post it. He's the cutest thing!