Like Antrax, Scratch had a long path to toy-hood.
In 1990, prolific TMNT character designer Ryan Brown pitched a set based on Edward Lear's 1870 poem "The Owl and the Pussy-Cat" - you know, really tapping into the hottest trends of the era. The main figure would have been a large owl who dressed like a homeless person, and he would have included a pack-in sidekick, The Cat Burglar. Playmates' Karl Aaronian rejected the submission:
The December, 1991 issue of Archie's TMNT Adventures comic (#27) a group of mutants colloquially called "the boogey-men" use mutagen to mind-control a small Massachusetts town, including a stranded April O'Neil, who manages to phone the Turtles for help. They drive the four hours up to Innsmouth and save the day, not realizing that the villains have survived. The story was written by Ryan Brown, and two of the mutants in the group were clearly his Owl and Pussycat characters (the third was a crow mutant, who was based on another rejected pitch, this one by Dan Berger). They were never named in the issue (well, the cat was called "Pookey" before it got mutated), but 1993's TMNT Mutant Universe Sourcebook dubbed them "the Uncanny Trio," and if you carefully read the indicia on the first page, you'll find their names are Nevermore the Scarecrow, Nocturno, and Hallocat. Probably because Archie wouldn't let them name him "Hellcat."
(It's easy to see how colorist Barry Grossman misinterpreted The Cat Burglar's prison uniform as a longshoreman's sweater and cap.)
By 1992, Playmates had come back around on the idea of a cat burglar toy, and had Ryan Brown resubmit it as a full standalone figure, rather than a pack-in.
Looking to promote the figure's release by having him appear in the Archie comic, Brown pitched a story featuring Scratch, which would have seen him operating alone (and possibly would have cemented him as being a different character, considering how different the two incarnations looked).
Also in 1993, Milton Knight drew "Coney Island Days," which saw the return of the Uncanny Trio in a very Looney Tunes-esque story. It was planned to be published in a TMNT Adventures Special, but then the series got cancelled, and the story never saw the light of day.
And so Scratch remained utterly obscure until the internet came along and the toy started trading for huge bucks. He did, however, have some influence on the IDW character "Old Hob" - not only in the sense of being a mutant cat, but also in that both their names are pseudonyms for the devil (hinting back at the suggested "Hellcat" name from 1991).
Scratch was also in the third Gameboy game, along with Scale Tail, which indicates that the designers just bought toys that were on the shelf and went with it.