No matter how much our culture expands its tolerance for sex and gratuitous violence, we are still fascinated by the nasty and the cruel in children's stories. Who doesn't like to tell the "real" story of The Little Mermaid or Sleeping Beauty to their kids once they've turned 10? I'm not immune to this fascination at all. The episode of Mr. Rogers' Neighborhood (1968-2001) about the nuclear arms race. The early episode of Adventures of Superman (1952-1958), starring George Reeves, in which the hero let's a few mobsters who've learned his secret identity die.
The Mysterious Stranger was not one of Twain's children's stories, assuming you believe The Prince and the Pauper and Tom Sawyer can be classified as such. I read it for the first time a couple of years ago and I saw that the story didn't teach me anything I didn't already know. Humans are more afraid of social condemnation than they are of doing evil. It doesn't take all that much to make us hurt one another, and not much more than that to kill one another. The book is a cackle from the greatest American humorist who had lived through slavery, the Civil War, Reconstruction, and finally the terrible birth of American imperialism, and who was on his way out the door. I wonder if it would have been better for the literary set in the Upper West Side to have read The Mysterious Stranger in the months after September 11 than Joseph Conrad's The Secret Agent. The Secret Agent is about "them." The Mysterious Stranger was about "us": the cowards who are too afraid to scream that a country that tortures in order to maintain its security probably has no right to exist; the cowards who are too afraid to admit that their government would bomb a village or two for 40 barrels of oil, as long as they never had to learn those villages' names. The Mysterious Stranger is the greatest fuck you of American literature.
The Mysterious Stranger is hilarious. If I were casting a live-action movie version, the title character would be played by Matthew McConaughey doing his nihilist act from True Detective. Just read this passage in McConaughey's voice and see what happens:
"Strange, indeed, that you should not have suspected that your universe and its contents were only dreams, visions, fiction! Strange, because they are so frankly and hysterically insane—like all dreams: a God who could make good children as easily as bad, yet preferred to make bad ones; who could have made every one of them happy, yet never made a single happy one; who made them prize their bitter life, yet stingily cut it short; who gave his angels eternal happiness unearned, yet required his other children to earn it; who gave his angels painless lives, yet cursed his other children with biting miseries and maladies of mind and body; who mouths justice and invented hell—mouths mercy and invented hell—mouths Golden Rules, and forgiveness multiplied by seventy times seven, and invented hell; who mouths morals to other people and has none himself; who frowns upon crimes, yet commits them all; who created man without invitation, then tries to shuffle the responsibility for man's acts upon man, instead of honorably placing it where it belongs, upon himself; and finally, with altogether divine obtuseness, invites a poor, abused slave to worship him!"
This claymation short is just as funny, but for entirely different reasons. You laugh because it seems misplaced. How dare anyone confront a child with such a nightmare! You also laugh because it's self-reflexive of the animation or claymation media, which are both predicated on the animator's ability to give life to inorganic materials. The hand of the animator was a powerful trope throughout the silent era. Winsor McCay's first short presented McCay himself as a hardworking craftsman who breathes life into Little Nemo by drawing him thousands and thousands of times. In Chuck Jones's Duck Amuck (1953), the animator is an abusive father. In Mysterious Stranger, the animator has become the devil giving life to organisms -- out of clay! -- who don't deserve to live. In The Mysterious Stranger, the animator reinvents himself as much as he does what appears on the screen. He's a cruel adult, but also a nasty little child. And his motives are never clear. The children stare out into a void, into a mise-en-scène that lacks any finitude.
Children would understand the message better than most adults. They love to mutilate their dolls.