From Drawn! is a link to a 1977 Doonesbury special that aired on network television. The episode (at least as it’s posted on YouTube) is broken up into 5 segments: part 1, part 2, part 3, part 4, part 5. The videos were added to youTube about a month ago, but have only been viewed less than 200 times.
You can read a bit more about the animation over on the IMDB web site.
Ah yes. Thanks for posting!
The film was later released theatrically and was nominated for Oscar.