The rubber sheets and the gerbils
I recently read through the original, unedited script and there was a scene in which the camera pans around to all the family sleeping. It shows Rocky and Ruby Sue sleeping, and suddenly there is the sound of shooting water as one of the kids is wetting the bed, right onto the rubber sheets that they are sleeping on. The camera then moves to the bedside table where the kids' have their pet gerbils in a cage.
I wish this scene would have been left in. It makes it even funnier when Cousin Eddie tells his wife, "Don't forget the rubber sheets and the gerbils", because the audience' minds automatically go to some perverse thoughts, only to discover that the statement was completely innocent and we, as the audience, are the ones with the dirty minds!