In the March 3, 1940 episode (the first one after the Yosemite episodes), Jack says that when Phil writes his girlfriend (Jack's erstwhile nurse) to "tell her that as a nurse, she doesn't know an aspirin tablet from a manhole cover."
Perhaps I'm reading too much in the line, but it reminded me of the saying that somebody who is clueless "doesn't know his/her ass from a hole in the ground."
So, aspirin <--> ass, manhole cover <--> hole in the ground.
Am I reading too much in the line, or was that likely one that got by the censors (or Standards and Practices, or whatever they called it in 1940)?