It matters less than you might think whether a puppy is the biggest or smallest in its litter! Of course, things like these will shape how a puppy behaves in its first weeks. Smaller puppies will often play a submissive role in their litter, whereas bigger ones tend to be more confident and dominant. At this early age, their character is not yet fixed, though, and it makes a big difference in what kind of family they find themselves in after being adopted. A big, boisterous puppy can learn to be well-behaved, and a small, timid one can quickly gain confidence.