user
Given a cartoon image and a caption. Caption: Please use a coaster. Question: Generating an explanation of why this image/caption combination is funny. Answer: 
assistant
People use coasters to prevent glasses from damaging wood surfaces like desks --- but here, the object that needs a coaster is a disembodied head. One would think that a person in this situation would comment on the disembodied head, but the man behind the desk is most worried about preserving the desk, and simply asks the head to use a coaster.