Phsstpok wrote: They took one of his Known Space stories, I think The Soft Weapon, and replaced the Kzinti with Klingons, IIRC.
It was The Soft Weapon, renamed to The Slaver Weapon, but it did not replace the Kzinti with Klingons. In fact, Niven rewrote it himself.
I found his line from the collection Playgrounds of the Mind about this:
The Slaver weapon is "soft" as Salvador Dali used the word: it changes shape. Those are "soft" watches in Dali's "The Persistence of Memory."
See "The Lost Ideas" for details on how this typical early-Niven puzzle story became a Star Trek animation called "The Slaver Weapon." I thought hard before giving the Kzinti to the Star Trek universe. I did it because I thought it would be fun to see what others would do with them. And I was right!
The section from "The Lost Ideas" in the same book about his involvement with Star Trek is:
I've had little involvement with movies and television.
Dorothy Fontana invited me to write a Star Trek animation. I feared (groundlessly) that nobody at Filmation would see their chance to use real aliens rather than actors in rubber suits. So I wrote a story treatment using Outsiders (built like a black cat-o'-nine-tails, using photoelectric metabolism at near absolute zero) and quantum black holes. For Saturday morning TV!
Dorothy advised me that wouldn't work. My next attempt was too bloody . . .
Dorothy and I presently spent part of an afternoon at Gene Roddenberry's place. Gene suggested rewriting "The Soft Weapon" from NEUTRON STAR. That worked, as "The Slaver Weapon," with Spock playing a Pierson's puppeteer. I was given permission to leave Kirk out.
My first attempt (quantum black holes) became the basis for "The Borderland of Sol."
And Paramount sold to Ballantine Books the right to turn my script into a book. Alan Dean Foster did that. So "The Soft Weapon" wound up competing with itself ...