I hope it is Ronnie Rocket, a script he wrote about a "Frankenstein-like creature who is re-made by two bizarre scientists."
I read somewhere that Lynch tried to get that going (before "Straight Story", I think) and said he couldn't make it work, so he dumped that project.
EDIT: Here's what I found:
Ronnie Rocket was a screenplay originally written by Lynch and possibly to star Michael Anderson (The Man From Another Place in "Twin Peaks" and the Woodsman (Twin #1) in " Industrial Symphony #1"), who would have played Ronnie. This was the first film Lynch offered CIBY 2000 as a part of his former three picture deal, but they elected to pass on it.
More information from Ann Kroeber, the late Alan Splet's (Lynch's sound designer) wife:
"Actually Ronnie Rocket was written LONG before David ever set eyes on Michael Anderson. The first RR script I read was written before "The Elephant Man" was made. He used to talk with my late husband (Alan Splet) and I , any chance he could get, about Ronnie during breaks of shooting "The Elephant Man." Ronnie Rocket was the subject that was near and dear to his heart."
"Ronnie scripts have gone through all sorts of permutations over the years. I suspect that "Ronnie Rocket" is David's most thought about story and may just never be made not because that production company didn't want to shoot it, they and several others were willing, but David wasn't."
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Ronnie Rocket (Tip Filmjahrbuch 1985)
"Lynch: Yes, I was asked to do "Ronnie Rocket" for him [Coppola]. I wrote that prior to "The Elephant Man' ; it was meant to follow "Eraserhead". I still love the story, but it`s obvious that it still needs a little work. I`ve just recently had a couple of new ideas.
TIP: Is it still the script that I read for, five years ago?
Lynch: No it`s entirely different, more popular.
TIP: A more commercial version of "Eraserhead' or simply easier to understand?
Lynch: Much more easy to understand and funnier. It`s got a lot of humour, an absurd kind of humour. It`s a rock`n`roll movie in a way.
TIP: Which kind of music?
Lynch: I exactly know which kind of music it is. It´s difficult to describe, you know, it doesn`t exist yet, but it´s based on 50s Rockabilly. Eddie Cochran, Jerry Lee Lewis, Gene Vincent...
TIP: So Coppola wanted to produce the movie.
Lynch: Yes. I had an office at his studio, and he said: "When do you come over and tell me the story of Ronnie Rocket?"
TIP: Tell?
Lynch: Yes, Francis is a strange guy. He wanted to sit down with his eyes closed and I was to tell him the story like a bedtime story."
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In the early nineties, Ronnie Rocket was to be produced by Ciby 2000 but it was dropped in favour of Twin Peaks Fire Walk With Me, the cast would have included Michael J. Anderson, and Isabella Rossellini: "I love the script, it`s simply great - very surreal, very funny, very strange, very emotive and in a way very touching as well. My role is just a minor one - but very funny. You never know what David is up to."
