Buck-a-roo! came from Milton Bradley. The idea was to load the buck-a-roo mule with picks, shovels and all kinds of stuff.
But if it got too heavy he would kick it all off and, er . . . you would have to start again.
Like Ker-Plunk! and Mousetrap, Buck-a-roo! was one of those games which used as many plastic bits as possible, thus ensuring they were unplayable after three days because some-thing would invariably go missing.