Speculah:Witches are generated by Magical Girls

There is possibility that the witches are generated by the birth of magic girls. That means the wishes can generate anti-wishes related to magical girls themselves. For example, Mami's enemies are related to flowers, butterfly, desserts. Mami has interests on desserts and she also uses butterfly-like hair clip. The theme color of the witches' lairs is close to Mami's theme color. When Sayaka becomes a magical girl, the witches's lairs changes to be in blue theme color. the stronger wishes generates stronger anti-wishes. That's why Kyuubey is not in hurry to let girls become magical girls. As a result, possibly Madoka could generate very powerful witches.