Any person shown to be interested may become a party to any civil action upon filing and service of an Appearance and pleading briefly setting forth his or her relation to the cause; or, upon motion of any party, such person may be made a party by order of court notifying him or her to appear therein. If a party, so notified, neglects to file an Answer or other responsive pleading on or before the date established by the court, that party shall be defaulted. No such default shall be set aside, except by agreement or by order of the court upon such terms as justice may require.