M and R talking during bathtime:
R: "It's a pain in the butt."
M: "Why is it called a pain?"
R: "If you say something is a pain, then you mean that it's annoying."
M: "Why do you say it's a pain in the butt?"
R: "It's just a figure of speech to say 'pain in the butt'."
M: "A butt?!" (lifts his bum out of the bathwater and points at it) "You mean like this little cutie?!"