Section 2001. Mistakes, omissions, defects and irregularities

At any stage
  of an action, including the filing of a summons with notice, summons and
  complaint or petition to commence an action,  the  court  may  permit  a
  mistake,  omission,  defect  or  irregularity,  including the failure to
  purchase or acquire an index number  or  other  mistake  in  the  filing
  process,  to  be  corrected,  upon  such  terms as may be just, or, if a
  substantial right of a party is not prejudiced, the  mistake,  omission,
  defect   or   irregularity  shall  be  disregarded,  provided  that  any
  applicable fees shall be paid.