Denotes a keenness or willingness to participate, in reference to a suggestion. It is generally said with contextually embellished excitement, and emphasis on the rhyming factor of the phrase.
This phrase draws its origins from the Pierrot, or 'sad clown'.
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi