user
Given a cartoon image and a caption. Caption: Beware the hidden service charge. Question: Generating an explanation of why this image/caption combination is funny. Answer: 
assistant
A reference to the trojan horse, which enabled soldiers to sneak into a fort undetected. Much like sneaking soldiers into a fort, hotels might sneak hidden charges into room service: the soldiers have seen this trick before, and are referring to how room service can similarly be a trap.