The puppy is barking at a ball as it rolls past it. You can remix and add more things for it to bark at (And also use some of the costumes that I left unused into your remix)
Dogsong - Undertale Dog Bark - Scratch Sound Library (I edited it slightly) Everything else by me The barking may be a little out of sync with the ball... I haven't found an easy way to fix that yet... (It also sometimes barks more than it needs to...)