user
Given a cartoon image and a caption. Caption: Personally, I think Prozac is a lot easier. Question: Generating an explanation of why this image/caption combination is funny. Answer: 
assistant
"As funny as a barrel of monkeys" is an idiom that refers to the plastic barrel of monkeys that's a children's toy. The delivery man is assuming that the other person ordered a barrel of monkeys to make himself happier, and quips that he feels that prozac, and antidepressant, might have the same effect, but be easier to use.