This is kind of mean, but nothing happens to your puppy. First, make sure your puppy is in front of the stairs. Second, heading for the stairs. You shoud have walked over your dog. It might take a few tries, but don't worry, you'll eventually get it. Trust me, I've done it tons of times, and I think it's funny and mean at the same time.
After you finish your fourth dog, you'll have to get rid of one of your three dogs. However you can avoid it by turning off your power.
To do this go to the park. Go to the section with the big tree. Make sure you're behind it and looking at it. Get the frizbee, and throw it at the tree. It should have gone through. This might take a few tries, but it's cool!
Hint: Make sure you can't see your person behind the tree.