I think Todd MacFarlane should do a Disney animated Horror film if Disney allows that.
I doubt they would, the very idea of a "Disney Horror" film, live-action or animated, just couldn't make it. One thing that keeps Disney going is their reputation for making family entertainment and this would definetely compromise them. I can't imagine a Spawn-like Disney cartoon!
Parents would be apopleptic. Fans would riot!

You think Eisner got heat, what do you think fans would do to Bob Iger if he ever produced something like that? The furthest Disney has gone in the way of horror (live-action) is Pirates of the Carribean and I doubt they would go further. (I mean under the Disney label, not counting M. Knight Shamylan's films under TouchStone)
In Disney Feature animation...it would NEVER happen. Especially now that a lot of viewers seem to be scorning the "new" animated film comedies/updates/parodies and clamoring for the "classic" stories like Cinderella and The Little Mermaid. An animated horror film, much less one done by Disney, just wouldn't happen. DreamWorks sometimes experiements with different things (just check out some of the human sacrifice stuff in Road to El Dorado) but they would never go all the way. Katzenberg has said very clearly that he wants to stay out of that territory, that he would never make an R-rated animated film. It's true you see a lot of that stuff overseas like in Anime and so forth, but in America I very much doubt it would fly.
EDIT: Forgot to mention Nightmare Before Christmas. THAT's as far as they'll ever go. I doubt they would have done Corpse Bride.
You can’t just have your characters announce how they feel! That makes me feel angry!