Dewey was the name of one of those three ducks, wasn't it? Huey, Dewey and Louie.
Also, I don't know if anyone has heard of the group America (they were aa 1970s group) one of the members is called Dewey Bunnell. Some of their songs were Horse With No Name, Tin Man, Ventura Highway, Muskrat Love. I like them.
I've always thought Hal was short for Henry or Harry, but it could be Hal's full name.