Final answer:
The phrase 'The Cat and the Pain Killer' is seemingly a reference to a literary work and could be a chapter from Mark Twain's 'The Adventures of Tom Sawyer'.
Step-by-step explanation:
The phrase 'The Cat and the Pain Killer' is most likely referring to a chapter title or segment from a literary work, rather than an academic text related to pain relievers like aspirin or oxycodone. Therefore, it is not directly connected to the content of '18.1: Pain Relievers- From Aspirin to Oxycodone', which falls under the purview of health and medicine, nor does it seem to be associated with 'Human Biology by CK-12' or the artwork 'Cat on the back' by Pbtflakes.
However, for readers of American literature, 'The Cat and the Pain Killer' may bring to mind the work of Mark Twain since it is reminiscent of Twain's satirical and humorous writing style. If this is indeed a reference to literature, it would likely be from Twain's 'The Adventures of Tom Sawyer', in which a scene involves Tom giving his Aunt Polly's cat, Peter, a spoonful of Pain-Killer, leading to a comedic turn of events.