Back in 1967, Norman Spinrad, who wrote one of the original series’ best episodes, The Doomsday Machine, had written another script called He Walked Among Us. Unfortunately, it was never filmed because the producer at the time had rewritten it as a (really bad) comedy due to Milton Berle being involved in the episode. The problem was that, even though Milton Berle was famed for his comedy, the script was never meant to be one, and Berle actually could do drama just as well.
Spinrad was disgusted with it, and creator Gene Roddenberry agreed that it couldn’t be made, thus it was scrapped.
So, 45 years later, when a fan came up to Spinrad with the original script, Spinrad signed it. The fan then sent him a scanned copy of the script, which is now available for purchase on Amazon. (Please note: this has nothing to do with the novel, He Walked Among Us, also written by Spinrad.)