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 in certain areas like Vault 101's entrance.

The player must either get Dogmeat later in the game or be careful that he does not die before getting this Perk because he does not respawn once killed unless you have this perk.