By the middle of the 1960s the big animation studios were in poor shape. Budgets had not budged since the 1940s, inflation was raging, full movie programs that included animated short subjects were dying and television was happy with productions that used good scripts and quarter animation. TV's audience (aside from Rocky & Bullwinkle) was kids, and they didn't notice the difference between Friz Freleng and Hector Heathcote.
Actually, we did, and we preferred Friz Freleng. It's just that we took what we could get. And in 1964, Howard Post got Jack Mendelsohn. Jack had been writing and drawing a strip cartoon, "Jacky's Diary". Jacky's Diary was drawn in the style of a six-year-old and filled with the misunderstood bits and pieces of learning that make up a six-year-old's understanding of the world and history. This meant that an unpolished illustration style could be brought to the screen at a much lower cost, and animation could be very poor and it would be exactly right for the cartoon. It would be cheap and well done.
There were only about half a dozen "Jacky's Wacky World" cartoons produced and Mendelsohn went on to a prosperous career. However, this silly cartoon about how the little Dutch Boy saved the city of Amsterdarn stands as a great monument to the fact that even during the darkest period of movie cartooning, people who cared could still turn out a great cartoon.