Well, it's not as simple as having just a couple of days available. In both films, Favs had to really slim down to play the role. He tends to let himself go more when he's not working as an actor, I guess. So He'd need preperation to do it and I don't know if it would be worth it for a small cameo role(which is what Happy has been and should remain). So unless Favs has changed his eating habits and now keeps up the slimmer look already, I doubt we'll see him as Happy.