Aaron Schreiber faces 41 counts in all, including 15 of making a bomb scare and ten of being a child sex offender working with children.
No trial date was a set. A psychiatric review was ordered.
Schreiber was previously found competent to stand trial; a ruling that pertains to his ability to assist in his own defense. The so-called insanity plea relates to his mental condition at the time of the alleged crimes.
A scheduling conference is set for April 17.
He allegedly made the threats to various businesses in the Waupun area in November, including calls to a school, a hospital and other businesses. Authorities also say he is a registered sex offender and allegedly violated the sex offender registry, by refereeing school sporting events.
Fond du Lac County also filed five charges of being a child sex offender working with children. A preliminary hearing is scheduled April 11 in that case.