Instructions
Go to the Bridge area of Halloween Town. Stand on the bridge and face the left wall. Align yourself with the chest on the wall and then jump to it. If you have the Glide ability, it is much easier to reach this chest.
Go to Guillotine Square. Walk to the mayor's house and look under the steps to find the second chest.
Climb onto the ledge across from the entrance to Guillotine Square. Turn around and face the large pumpkin head in the middle of the Square. Jump off the ledge and glide into the pumpkin's mouth to get the chest.
Return to Halloween Town after beating the boss and sealing the keyhole. Go to the Cemetery and walk to Moonlight Hill. Enter the new door that has appeared. Open the chest inside to free the puppies.