I’m not convinced.
I don’t get the cartoon either, but I see from the header that it is supposed to be some kind of medical humor, something a doctor would get. That’s the major clue.
Second, you could make a joke about omitting the L from “clock” without making any sort of reference to Mr. Ed the talking horse, whom some of us do remember from the very old TV sitcom.
If that were the joke, then, there’s no relevance to doctors and no relevance to Mr. Ed, who is pictured on the wall behind the two men. Also, even in the context of the joke, it does not seem as though an error of that sort would lead to a “swift and ignoble” end, just embarrassment.
I would look instead to someone who could tell us what phrase in the world of medicine bears a close resemblance to some portion of the phrase “Mister Ed Talking Horse Clock” and means something horrible enough for a misprint to be fatal. I am going to go all out and put down a quarter that says it isn’t “cock.”