user
Given a cartoon image and a caption. Caption: Dr. Ogden just called to say your mercury levels are on the high side. Question: Generating an explanation of why this image/caption combination is funny. Answer: 
assistant
When doctors treat older humans, they measure things like cholesterol, blood pressure, etc. But, in this odd world, the walrus is being treated by a human doctor, and his medical problems are related to mercury, which is a problem for sea life like fish. The woman looks on disapprovingly, almost as if mercury levels were affected by the walrus sneaking unhealthy foods.