Wis. Stat. § 891.32: Allegation as to representative capacity.

Whenever a plaintiff sues as a personal representative, guardian, or trustee and alleges in the complaint appointment to that position and, if the appointment was made in another state or a foreign country, the filing or recording of the authenticated copy of the appointment as required by the laws of this state, those allegations shall be taken as true unless specifically denied in the defendant’s answer.