GAGE to POOP.

Every letter change

1. GAGE → CAGE: change letter 1 from G to C.
2. CAGE → CAME: change letter 3 from G to M.
3. CAME → CAMP: change letter 4 from E to P.
4. CAMP → COMP: change letter 2 from A to O.
5. COMP → COOP: change letter 3 from M to O.
6. COOP → POOP: change letter 1 from C to P.