Main characters have, um, diversified a bit recently. Point of views have as well. Human beings used to have the market cornered as far as main/primary characters were concerned, but we're limited only to our own imaginations. Adults, aliens, animals, supernatural creatures, children, inanimate objects. We've seen them all, but what makes a non-adult (or non-YA, in most of our cases) MC work?
One example from the, gulp, sixties is the fabulous Mr. Ed.
Not from a book, but still a classy main character with an attitude. Ed showed us that main characters can get into all the same predicaments humans can, even with two extra legs and those crazy, bowling ball eyes. As an aside, if you haven't seen the recent movie, Arthur, with Russell Brand, his horse-phobia is probably the most hilarious part.
If the show had focused strictly on Willlllburrrrr, hehe, sorry, Wilbur, with Mr. Ed as only comic relief, we may have loved it less. It's because Ed was chosen as the MC that we care about Wilbur's life.
In our writing, we have tons of options for who will be our main character and our narrator/main POV. Look at your WIP. Could you benefit from writing it in third person? How about from the perspective of the villain? How much more insight would you gain about the MC (assuming the villain isn't the MC) if you tried that?
We'll pick up with this discussion on Friday. Maybe I'll use Alf as a second example. LOVE ALF!