If, while arting, one chooses to portray a member of the Kingdom Animalia, chances are an eye or two will be necessary. Maybe even eight. No matter the number, a piece of art with eyes has arguably more potential for charm and emotion than other genres of art. I'm not ragging on landscapes or still lifes, but living things draw our attention and our hearts. It's why the human figure is portrayed so often. It's why we love our pet dogs and cats more than our houseplants (if we aren't N, that is. He loves his Starfruit tree "Fwang" [yes, he named it] more than just about anything).
Whether of a person, a pet, or wildlife, art with eyeballs is tough. The eyes are the key. They are the conduit between the artist and the viewer; the soul of the art. If you get them right, nearly all other mistakes can be forgiven. And if you screw them up, then forget it. It won't matter if everything else is perfect, the piece won't work. That's why some artists complete the eyes first thing, so if they screw up, they don't have much to redo.
I don't usually do the eyes first - in fact, I often leave them until the end. I love adding the soul to a piece by working on the eyes. Leaving them until the end keeps me motivated. Often I'll think, "I'm nearly done, and this still looks like crap!" Then I fix the eyes and everything works. Some good examples of eyes that make the piece work, even though there are flaws in other areas:
Eyes that don't really work, and bring the whole piece down:
At this stage, I seriously considered changing my skin tone to pallid deathly green and writing "BRAINS!" across the top in bright red. They're all shiny from the flash, but even without that, I look like a zombie. After some good advice from WetCanvas and some plain old *looking*, I got them better. And yes, this is the dreaded self portrait in oils. It's done enough, and I'm not opening those tubes again, ever (or until I forget that I hate them, which will probably be next week).
So, eyes matter. The few portraits I've done are of people and animals I knew well, or see every day. Their eyes were very familiar. After I got a few nibbles on portrait commissions, I wondered, would I be able to get their eyes right? I don't even know these people! Hell, I can't even get my own eyes right, and I see them every day. Maybe this time, I'll do the eyes first.