In retrospect, a warning was definitely warranted. I apologize for not including one. I definitely had a lapse in judgment not doing so.
However, I stand by my decision in including it. Despite the blue theme, it is a good example of the remix culture that I often discuss. Not only did Jonathan Coulton release the song in question, along with the rest of his works, under a CC license, but he also produced the karaoke version that was used by the project expressly with the intent of people remixing it. Part of the intent of the project was to help raise awareness for the Joe Murphy Memorial Fund.
I will re-tag that episode as adult, update the show notes and, if I get a chance, update the audio itself to add an appropriate warning.