...would have been as funny if Oliver and Lisa fixed the house up?
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the Clampetts are in a fancy Beverly Hills jewelry store. Granny points to a tray of rubies.
Granny: "How much fer one o' them red diamonds?"
clerk: "Madam, those are rubies."
Granny: "OK ask her kin we buy one offa her."
clerk: " The ruby I am talking about is not a lady."
Granny: "Lissen, how she got them diamonds is her business. I'm just sayin' ask her kin we buy one from her."
They did try. The improvements made throughout the first season (porch railing, expanded bedroom, new fireplace, new closet, telephone, etc.) remained for the duration of the series and their pitiful state coupled with the rest of the farmhouse provided background surrealism. So even when a joke wasn't directly referencing any of these things a viewer gets these constant reminders of how ridiculous and absurd this show is.
Also, the Douglases keeping the same luxury furniture they had in the penthouse and cramming it into their dilapidated shack just added to the surreal experience.