"Have you ever ‘auditioned’ characters to see who your story’s Protagonist was? Started a story with one Protagonist, then found the story drifted over to another character?" I've never "auditioned" a character but I've definitely found that a protagonist I originally went with is outshone by a lesser character. That can be equally exciting/frustrating. Exciting because you've found the right protag, frustrating because I usually don't find out until I've written the script with the original protagonist. Although as my first draft is my version of index cards, it's not that much of a bad thing.

I like this idea, too! “Have you ever ‘auditioned’ characters to see who your story’s Protagonist was?" Yes and No. As a writing (/thinking) exercise, I like to go through the Shakespeare plays and see what happens if I make one of the "other" characters the protagonist, and then work through that story.