I got a great question from Sergio, who wrote in to ask: "How do you find your reference for an unusual four-legged character and how do you do your planning for the movements?"
Hi Sergio! First off, thanks for the great question!
I know that's a tough thing that a lot of newer animators struggle with. You have to animate a dragon or a dinosaur or a centaur, but for some reason, there just aren't any centaurs to be found at the zoo.
Well, this is one of those times that you're going to have to put your animation imagination into overdrive, but that doesn't mean that you shouldn't study any reference!
What you want to do is look for animals that have a similar physical makeup to the creature you will be animating. Sometimes this means studying multiple creatures.
An example that comes to mind was Eragon. When we were animating Saphira the dragon, we noticed that her body was very similar in proportion and design to that of a lion, and her wings were designed very similar to eagle wings.
We got right to work amassing a lot of great footage of lions and eagles and started studying the heck out of them, looking for concepts we should be using in our work, and studying how their body mechanics worked. When Saphira was on the ground, we tried to take inspiration from the movement of the lions, and in the air we animated her wings in an eagle-like pattern and fashion.
So just take a long look at your character, and see what it reminds you of, and start investigating the animals out there that might be similar. You can find great reference on Animal Motion Show (Rhinohouse Dvds), youtube, documentaries, movies, BBC motion gallery, etc.
The important thing is to base the movement (and acting) of your creature on REAL LIFE ANIMALS so it will have believable body mechanics that an audience can relate to and accept easily.
Hope that helps! Good luck!