What is the most adorable puppy?

The book I'm writing right now has brother and sister puppies. They need to be different colors, but clearly from the same litter. They don't need to be purebred, but I'd like to describe them by referencing a dog breed people are familiar with or can look up, i.e., "They resembled Labrador retrievers..."

With that in mind, what breed of dog has the most adorable puppies? Please support your case with photo evidence.