I just saw an example of another exception to the rule. Tales from the Far Side. By no means is it bad, or poorly done by any means, but it's just...off. It's a brilliant piece of animation if you take it for what it is. Somehow it feels like Courage the Cowardly Dog (specifically the early shorts and first season) without the family, but overall the humor of the special isn't any improvement over the one panel strip. In fact, with more context, the jokes have a different tone, less of funny and more of actually creepy. One segment features a drunk wolf watching footage of his mate on an old movie projector, gradually ending with his mate getting caught in a bear trap was just depressing. Probably the intent, but a miserable wolf dulling the pain sitting in a dark room watching old home movies to the tune of "I'll remember you" (or whatever it's called) is just disturbingly tear jerking and completely out of tone with the comic strip.
There's like a thing about aliens disguised as cowboys and a way to tell them apart that actually needed to work in animation (or a multi-panel strip)... that's it.
It's a beautiful film, sure, but completely unnecessary. Probably why there was only one of these and it fell into considerable obscurity.