Both of the following are weighed evenly to the Anna and Eve scenes. So as long as you meet the conditions, they should each have a one in six chance of triggering when calling on someone at random.
Misaki under table conditions:
Requires that you own the following characters: Misaki, Mitsuko, Sidra.
Breakfast only.
Mitsuko under table conditions:
Requires that you own the following characters: Misaki, Mitsuko, Sidra.
Breakfast only.
Hope that helps.