Puppies!

 is a perk that is to be added to Fallout 3 with the Broken Steel DLC.

With this perk Dogmeat is reincarnated as a puppy every time he dies and can be added back to your group when the "puppy" goes to Vault 101. Dogmeat's puppy seems to be much tougher than the original Dogmeat.

Despite the name, this perk only allows you to get one Dogmeat's puppy at a time. If it dies, it will be replaced by a new puppy.