FOES to POOP.

Every letter change

1. FOES → DOES: change letter 1 from F to D.
2. DOES → DOER: change letter 4 from S to R.
3. DOER → DOOR: change letter 3 from E to O.
4. DOOR → POOR: change letter 1 from D to P.
5. POOR → POOP: change letter 4 from R to P.