Guide to Frog Zone

Frog Zone is one of the rarest achievements in the game, but isn't actually that difficult. The main factor here is the convoluted unlock condition; Frog unlock attempts can be tried as soon as Mom can be semi-reliably beaten in loop Sewers.

Frog cannot be truly unlocked, but rather if any character has the Golden Frog Pistol (GFP) as their starting weapon, a run will instead start as him. As a golden weapon this means it's a temporary unlock and can be overwritten, which will require this process to be repeated. GFP can be transferred to other characters using the Proto Chest, which can be used as a backup.

Short Summary: Defeat Mom in loop Sewers while having any golden weapon on hand. This causes her to drop a Frog Pistol, which can be stored in the Proto Chest. On a new run it will now be the Golden Frog Pistol instead, which will be unlocked on that character.

Frog Pistol
 Golden Frog Pistol

Step by Step:

  1. Start a run using any character that you are proficient with. GFP will not be unlocked on this run.
    • If unsure of who to run then pick Chicken. Her passive makes the game more forgiving and she can throw weapons into the exit portal when needed.
  2. The first goal here is to reach L1 Sewers while running any golden weapon and any crown.
    • Golden weapons are random drops in loop making this unreliable. There are two options to remove RNG;
    • Use a starter golden weapon all the way to L1 Sewers, which can be limiting to the run.
    • Leave a starter golden weapon in the Proto Chest in the 3-2 Crown Vault in preloop, which requires starting the run with any crown. This can be retrieved in the 1-2 L1 Vault which will minimize the levels needed to clear with it. Do NOT visit the 5-2 Vault on this run.
      • If three Vaults are visited in a run then they will no longer spawn, so visiting the first three will make this a failed attempt.
  3. Once L1 Sewers is reached then Mom can be killed while having a golden weapon on hand.
    • Some guides will mention damaging Mom with a golden weapon at least once. This is not required, but it can still be done for ease of mind.
  4. Mom will drop a Frog Pistol on death. This can be swapped out with whatever golden weapon is being run, as it is no longer necessary.
  5. Continue to the 3-2 L1 Vault while having the Frog Pistol on hand.
  6. In the 3-2 L1 Vault a Proto Chest will spawn due to running a crown. The Frog Pistol can now be stored here, and the run can be exited.
    • The weapon will auto-store and the Vault level does not have to be cleared, though can still be done for ease of mind.
  7. A new run can be started, choosing a character that you will unlock the GFP on.
    • Chicken and Rogue are popular choices as they have unique starters, thus can easily waste their golden weapon slot.
  8. Reach the 3-2 Vault in preloop while running a crown, or take a crown here and reach the 5-2 Vault.
  9. The Proto Chest will have changed the Frog Pistol into a Golden Frog Pistol. Take it and enter the following level, which will unlock the weapon with that character.
  10. Starting a run with the Golden Frog Pistol will now unlock the Frog Zone achievement!

Frog has his own character page which gives a guide to all Frog-related tech as well as strategy guides, as well as how to play as him on dailies.

Here is the Step by Step visualized. If the 3-2 L1 Vault is destroyed on accident, then any later Vault also works.