Concept art of an older version of the twins.
The TMNT 2003 series was the second television show based of the Mirage comic book. It is known for having several dark episodes including the infamous "Insane in the Membrane". But there is one episode that was so dark that it was never completed.
Titled "Nightmares Recycled, the basic plot involves Raphael, Donatello, Casey Jones, and April O'Neil encountering the Garbageman(a minor villain who appeared in only two episodes). They are taken to the Garbageman's Recycle World and later encounter Hun. Hun isn't thrilled to reveal that him and the Garbageman were once conjoined twins. According to the script, Hun and Garbageman were conjoined twins who were separated by a shady back-alley surgeon. The Garbageman was discarded as 'garbage'.
The episode was already beginning to be animated when the plug was pulled. 4kids claimed the subject of the episode was too violent for a children's program. Peter Laird later criticized the script on his blog (the page is now inaccessible). Later on the shows' Fifth Season as a whole was left unaired until 2008. The script in full has never been released.