So there is still one open question remaining about Madoka….

who is that f*cking cat? (in the opening)

???

Edit: found the answer:

[…]drama cd 1 from DVD volume 1 explains the black cat 

timeline 1 Madoka became a magical girl to save a dying cat that was hit by a car

however, she keeps this a secret from Mami, who would otherwise scold her for becoming a magical girl for such a “half hearted reason […]”

further reading:

http://kurogane.animeblogger.net/2011/04/26/madoka-magica-drama-cd-01/

 Bonus: