The worst character on this show is...
Muffy.
And yes, I'm aware I'm a grown man talking about a children's show. Well, guess what? I was a kid when this first aired and I used to watch it.
Anyhoo, Muffy is hands down the WORST Arthur character as she's your stereotypical rich kid... which makes me wonder, if she's so rich, why does she go to public school?
She is greedy, vain, stuck-up, cocky, a diva, and a straight-up BEE-OTCH.
I've disliked her from Day 1, and how she treated Francine in the school picture episode.
And speaking of her treatment of Francine, remember in "Prunella Gets it Twice", Francine is trying to get money to buy Prunella that doll, so she goes to her "friend" Muffy who has more than enough to spare, but she outright refuses. She practically dangles the money in front of Francine and then pulls it away.
Let's also not forget Muffy showing her anti-semetic side in Arthur's Perfect Christmas, saying Hanukkah wasn't as important as Christmas and then giving away Francine's gift.
This character is insufferable. And worse yet, I heard a rumor they were going to give her her own show. How would you even build a series around a character like Muffy? They couldn't build one around Buster, and he had more character development than Muffy... though, Buster's show was really nothing more than home videos of different locations sandwiched between a few animated scenes of Buster and his dad... but how could they do a Muffy show? Unless maybe it's a riches to rags story of her family going broke and she has to live like a normal person?
I realize not EVERY character in a children's show needs to be a rolemodel, as there are always those people among us who never learn their lesson, and Arthur's answer to that is Muffy. And I know she's just a third grader and mostly influenced by her parents, so I'd cut her a little slack.