Before Paul Frees did the voices of Ludwig Von Drake, the Haunted Mansion's Ghost Host and a lot of the other voices he's famous for, he actually did a few voices at Disney in the late 1940s and early 50s. For instance, in the Donald cartoon CRAZY WITH THE HEAT, he voices the translucent Arab that Goofy meets. In the Pluto cartoon PRIMITIVE PLUTO, he voices the little wolf that poses as the dog's "primitive instinct". It says so at IMDB.
