I like Judith. She's only in one episode, and very little is really known about her, so I've made up a lot of stuff and made her up to be a more enjoyable character. I can't stand the thought of both of Bob's parents being as evil as he is in the show (they were willing to help him murder a child!) so I just pretend the bad stuff never happened. In "Funeral For a Fiend," Marge has weird dreams, and then Bob does, so I like to assume the entire episode was just one or more people's crazy dreams.
Judith is featured in several of my deviations as a loving mother (and, appropriately, a drama queen).
I had the same trouble with Bob and Cecil at first, but once I started RPing, everything changed. When you play a character, you essentially become that character, and pretty soon you are able to meld your own thoughts and feelings with that character's, so that you can make him or her totally relatable to you. Or if you simply write a story about them. Writing really puts you in their mind.
We're still working on it. In fact, now that she's settled into her new home (just moved last week) we just now restarted it, but if she doesn't mind I can maybe send you the part where Ernie is first introduced and kidnaps little Cecil.