This new Star Trek show had a lot going for it. Many of the original writers from the original series came back to write new episodes and sequels to their live action episodes. These included "More Tribbles, More Troubles" by David Gerrold which was a sequel to his "The Trouble With Tribbles" episode. Chuck Menville and Len Janson wrote "Once Upon a Planet", a sequel to "Shore Leave" written by Theodore Sturgeon. Stephan Kandel, author of two Harry Mudd episodes of the original series, returned to pen an animated Mudd tale, "Mudd's Passion". Even actor Walter Koenig, who had portrayed Ensign Pavel Chekov on the original series, wrote a script, "The Infinite Vulcan", which tied in to the original series episode "Space Seed." D. C. Fontana, who had written some of the most memorable episodes of the original Star Trek series, contributed a script which would be recognized as one of the best Trek stories written, "Yesteryear". Fontana selected writers that would be able to maintain the quality and consistency of the Star Trek concepts