How would a Rex game even work? Does Rex have the mind of a human? Would he walk around with human inner dialogue? If not then it would just be....Food, food, food, food, sex, nap, food, OH LOOK A SQUIRREL!!!, food, food, nap, food, food. That's pretty much the extent of a dog's thinking. The Rex stuff is fine for short animations, but with a full game you have to apply some kind of logic and that's difficult to do unless you're going full furry style anthropomorphic or something werewolf related.