RCW 4.68.050: Pleadings.

If the defendant in his or her answer, deny the judgment, or set up any defense which may have arisen subsequently, the summons, with the affidavit annexed, and the answer, constitute the written allegations in the case; if he or she deny his or her liability on the obligation upon which the judgment was rendered, a copy of the original complaint and judgment, the summons with the affidavit annexed, and the answer constitute such written allegations.