Puppies!

 is a perk 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 either by finding him resurrected at the location of his death or by waiting until he is moved to the Vault 101 entrance. 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.

This perk still works if Dogmeat died pre-Broken Steel.

Glitches

 * Firing a follower such as Fawkes with one of the puppies in-tow may make it impossible to re-hire them, as they will act as though you have another follower when you ask them to follow you again. This is a glitch and it appears to occur for some even if Dogmeat's Puppy is dead or waiting outside Vault 101. This means that trips to The Pitt should be avoided if you want to be able to rehire humanoid followers, since all followers automatically get fired when heading to The Pitt. (I found a solution for this. Tell the pup to wait outside vault 101, and when he gets there go into VATS and shoot him in the head. When you leave VATS you should get a message notifying you that your followers have returned to their default locations.)
 * Mod fix for PC users now available: ]


 * It is possible to get all followers by exploiting the Puppies! perk. Get Dogmeat or his puppy and tell him to go back to Vault 101. When he starts walking away reverse pickpocket a mine or grenade into his inventory. Then go hire your follower and wait for Dogmeat to respawn. Rinse, repeat. NOTE: You must be in the same cell(room) as the follower you want to hire when you kill Dogmeat. (In my experience, doing this for Fawkes made him invincible.


 * You may have to wait weeks at a time to get a new puppy, or sometimes a new puppy may never come. This is the case of the puppy dying in strange areas, or not loading in previous areas.


 * Because Dogmeat's Puppy respawns at the location of his death, waits there for an indeterminate amount of time before being moved to the entrance to Vault 101 many people are finding it difficult to locate him, especially confusing because the message that indicates he is waiting at Vault 101 appears whether he is there or not.


 * After the puppy spawns at Vault 101, it may become stuck permanently in the ground (confirmed Xbox 360). It will act and move as if it is fine, but upon interacting with it, the puppy will behave like a corpse, allowing you to loot it, but it is carrying no items. This makes speaking with the puppy impossible. If this happens, attempt to reload your file from any previous save and retrieve the puppy again. This may not work, however, resulting in the puppy becoming useless. You could reverse pickpocket a grenade and kill it.(Unconfirmed)


 * If you do not have a follower when you get the Puppies! perk, it may not be possible to re-hire any followers except Dogmeat, even if you don't have Dogmeat or Dogmeat's Puppy in your party.


 * It might be possible to fix this by killing Dogmeat's Puppy and hiring your desired follower.