Winston was an adorable but mischievous dog, and the pet of Mr. Bertrin Braithwaite. Whether he was a puppy or a full grown dog is unknown. During the events of the arc, he and his owner has just recently moved into a house across the street from The Jenkins' House.
Winston may have meant no harm, he may have thought the needed to protect his home. Therefore he was very unfriendly and vicious to Grandma Jenkins. She is the neighborhood letter carrier and she was just minding her own business trying to deliver his owner the mail. Then during the course of a couple days. he growled and barked at her. He chewed and gnawed on her pant legs. Grandma Jenkins tried distracting him, throwing him bones and petting him. Usually he would end up either end up breaking into her groceries or chasing her out of the yard.
Eventually, when his owner accidentally sprayed Grandma CeCe while watering the lawn, he found out how upset she was from him. Then soon enough Winston and Mr. Braithwaite visited Grandma CeCe apologized and made amends and he turned out to be a very affectionate dog.