In modern games, I think it's fairly common to have a common 3d skeletons share names. So you can make animations like the one above apply to any character even if they have differences. It doesn't mean that dog extends human, but it may mean that a dog model shares a lot of common "bones", that are used for movement, with a human model.

So when a human animation is applied to the dog, you can see it warp to start position of the animation, move, and then then stop at the end position as a standing human, before warping back to idle animation (when it turns back into the dog shape)

Related, weapons in Destiny also share the same components across weapon types, and bugs have caused one weapon type to be used for another weapon, making funny things happen. Like how a hand canon (pistol) stretches like a bow because it's model got used in place of the bow model at the start of this clip:

https://www.youtube.com/watch?v=0YZa9vv5U0M