What’s the worst message you’ve seen?

Nothing should be erotic in children's media.

>kidnapping is... LE BAD
>identify theft is... LE BAD

It’s about finding passion in your work by not letting work be your whole life. Jack loved the idea of Christmas but his talents weren’t suited for it. In the end he realized that he needed only have a break from the monotonous routine of Halloween in order to find pleasure in it again. Christmas still became a part of his life in the end, which is all he really wanted.

Was the character in the show writing this fanfiction for children?

uh, they are

>it's about being devoted to your given role and doing a bit of consuming on the side to stay sane
Pretty bleak when you put it like that

What's bad about this one?

>in a very heavy handed way
I can already tell who's the blue hair writing this.

It's low-hanging fruit, but the episodes Seahorse Seashell Party and Screams of Silence from Family Guy. The first episode says that it's a good thing to stay in an abusive relationship for your abuser's benefit. The second (the very next episode, mind) tries to play domestic abuse completely straight (probably in an attempt at Emmy bait), but it gets so much wrong, including the message that if you just kill the abuser, everything will be fine.
I know it's Family Guy so it's possible it was all done tongue-in-cheek, but they still sucked at it.

Why would it? It was explicity shown that Jack's naitivity and wanting to pull off Christmas in the only way he knew how had major consequences.