I read this in the mid-late 1980s, it was a paperback children’s book with soft purple cover, illustrations of cat and duck on front. I remember there were flap pages inside. The story was along the lines of a lonely duck and cat living in the same neighbourhood, I think a ball goes over the fence of one of their houses and they end up becoming friends. I think the kitten wore a hat? And the duck wore a dress? But I could be misremembering the clothing details. The cat was black/white and duck was yellow