Katherine Thiggings (née Davis) is the mother of Madison, the girl PJ was dating. She's also ex-girlfriend of Bob Duncan. Hardly anything is known about her, because she only appeared in one episode. Bob Duncan nicknamed her Kitty Cat, and it is revealed that she was the last girl Bob dated before Amy, and Amy does not like when Katherine comes over, for she is somewhat disgusted. ("Boys Meet Girls").
She is friendly to Bob, but is secretly jealous of Amy. She is still in love with Bob, and her nickname for Bob is "Bobby".
Amy is seen to be jealous of her due to the fact that Bob calls her "Kitty Kat". Amy suspects that the couple still have feelings for each other. Katherine is very demanding and possessive. She loves Bob after all these years, and It is probable that she regrets the breakup between her and Bob.
She dated Bob in the past, and they broke up for the same reason PJ broke up with her daughter Madison- Cause they were interfering with PJ and Bob's friendships and bands. It is unknown who she married since her daughter Madison came to be. However, she is still friendly to Bob and calls him "Bobby". She has not been seen or heard of since Boys Meet Girls)
Bob Duncan is her ex-boyfriend.
Madison is her daughter.
Katherine still has feelings for Bob.