Heart of Karl is one of my favorite horror movie shorts. It's one of the few that I think deserves a full length treatment. The film doesn't spell everything out for you; it focuses more on atmosphere and special effects.
The central relationship is between Karl, who looks a little like a cross between the Joker and Freddy Kruger, and his brother. I'm not exaggerating when I say this film unfolds like a collaboration between the makers of Silent Hill and Ernest Hemingway.
The story delivers on all fronts: it is effectively creepy, but also got me to care about the characters. Except for Karloff as The Monster, I don't think there is another movie creature I enjoyed as much as Karl. It also has some scenes that are exactly my preferred style of humor. It may have been a low-budget film with some dated animation, but I can watch it over and over. I liked the music, the performances, the atmosphere, I liked it all. 8 out of 10.