It's been a bit of a problem for me: Leonard and Celia didn't look a whole lot like deer, but still some kind of weird hybrid animal. It's mostly been in their heads, followed closely by their constantly-changing, never-the-same hooves.
So in response, I spent a couple hours yesterday afternoon scrounging Google and deviantART for images of deer to use as reference. I initially based them on Whitetails, but as soon as I glanced at the first image of one, there were outstanding issues.
Bah, you're probably not really interested in the backstory. Long story short, I made changes to both Leonard and Celia to make them reflect the animal they're based on. I ditched Leonard's awkward "4" antlers for something a bit more realistic, and added some characteristic traits of Whitetail Deer, such as the white chin and end of the snout.
I also fixed those ears. Good god, the ears.