They should definately put aliens in the game. They should also make it where you can meet them in more levels other than just two. They should make them harder to kill, they were WAY too easy to kill. You should be able to kill them by being able to use different fighting moves where you can grab their tails and swing them. Also being able to pick them up and smashing their head in the ground. That would be hot.
They should have the aliens be able to jump on you and try to headbite you and you have to struggle and get them off you before they're able to do it.