user
Given a cartoon image and a caption. Caption: When you don't want one, they're everywhere. Question: Generating an explanation of why this image/caption combination is funny. Answer: 
assistant
A joke about the difficulty of finding a cab when you need one, and the ease of finding one when you're not looking for one. This joke takes the idea to an extreme: here, the men are not seeking a cab, and are even inside of a building, and cabs are so comically abundant that one is coming up the stairs.