When this thing first came out, it was no internet meme--heck, there was no internet--so parents would pick it up as a Beta videotape, think "claymation=wholesome family fun," and plunk their children in front of the tube for awhile to watch it. I even know folks who had this movie shown to them in elementary school.
I have read that they often censored this segment for television, but that's a bit like closing the barn door after the horse got out, isn't it? The damage has been done; you will never be able to read Mark Twain again, at least not normally. The Prince and the Pauper? Satan. The Adventures of Huckleberry Finn? Satan! The Celebrated Jumping Frog of Calaveras County? Also Satan!
I can only speculate that this was a movie intended to dissuade any future English majors. See where a literary life of the mind has left Mark Twain, kids? He's despondent on an airship, determined to destroy himself and his own creations by exploding into Halley's comet, while hallucinating a claymation apocalypse! Is that what you want for your life? Doesn't an accounting major seem much more pleasant now?
Satan's a sorry name for an angel.
The Adventures of Mark Twain. Dir. Will Vinton. Perf. James Whitmore, Gary Krug, Chris Ritchie. Clubhouse, 1985.
Adventures of Mark Twain