Who or what are Henry and Hetty Hoover (not to mention Harry)?

One evening during a trade show in the mid-1970s, Duncan and a salesman, bored, dressed up one of their current commercial machines with ribbon, a Union Jack badge, and something like a hat, then chalked a crude smile under the hose connector. The next day visitors noticed it and laughed; Duncan then decided to ask his advertising people to design a proper face; they nicknamed the result "Henry". At another trade show a children's hospital was interested in the cleaners to encourage the recovering children to help with the cleaning. Production, still focussed on the commercial market, was increased.