As for the whole animals thing, they originally wanted to have the characters riding horses on the show, but the game maker told them they couldn't do horses so they weren't able to include them. So at least at one point in the development they were still going to have some Earth animals around. Have we seen any dogs in town?
The who thing with the game not being able to have horses seems weird to me though, we've gotten tons of games over the last few years with the characters riding interactive horses, including all of the Assassin's Creed games since II, and Red Dead Redemption. Would it be something to do with the fact that it's an MMO?