Glad so many of you enjoy the "backstory."
As for how they "got" to use him, that I don't know, but I would be willing it was more of just another "easter egg" placed by an animator as a tribute to Don Knotts. There are LOTS of hidden things in "The Little Mermaid." It is a film that has more than any other Disney film to my knowledge.
Some of you may remember the original VHS case artwork had to be redone, tapes were recalled, and reissued due to some animator "fun." (I have one of the original covers --- it's on the shelf behind me as I type.) Of course, some argue there is nothing intentional on the cover, but nonetheless, Disney revoked them all and reissued.
Among other hidden things in "The Little Mermaid," if you know just where to look, you can spot Mr. Limpet, Mickey, Mouse, Donald Duck, Goofy, Kermit, and an older man that some will argue is meant to be Walt himself. There is also a person wearing mouse ears and a Mickey balloon.
Lots to hunt for in "The Little Mermaid."
- Dreams