If a third person claims the property or any part thereof, the plaintiff may amend and bring the third person in as a codefendant, or the defendant may obtain the substitution by the proper mode, or the claimant may intervene by the process of intervention.
Iowa Code § 643.4
Interpleader, R.C.P. 1.251 - 1.257
Intervention, R.C.P. 1.407