Wis. Stat. § 801.51: Challenges to improper venue.

Any party may challenge venue, on the grounds of noncompliance with s. 801.50 or any other statute designating proper venue, by filing a motion for change of venue:

(1) At or before the time the party serves his or her first motion or responsive pleading in the action.

(2) After the time set forth in sub. (1), upon a showing that despite reasonable diligence, the party did not discover the grounds therefor at or before that time.