A phrase used in a flirtatious context often preceded by a question as to whether or not something is meant to be "dirty or not". It is used as a diverting comment so the person will be distracted.
Girl: Hey you :) what's up?
Guy: You mean what else is up? ;)
Girl: Was that a dirty joke?
Guy: You tell me... all i know is that the pepper hit the fan about ten minutes ago. :)
Girl: Oh man...explain that one..