The starting pet is always unique. The rest are just monsters. In the first game, we were given a green, one-eyed, winged beast-thing. Now we have a pink fox with blue marks on its back.
To unlock characters, you have to reach a certain amount of kills for each one. 1000 for Nat, 3000 for Lance, and 10000 for the last one (I haven't unlocked him/her yet) + So people can see this.
Decent, however needs improvements. Not much excitement, little balance, no realism, and overall boring. Needs major improvements. Uzi is not that slow or powerful, and it doesn't have such a small clip. If there was a faster pace, (more spawns, strategy, and difficulty) then it would be plausible and would have a great improvement. 2/5. Next time, work more on the game, and don't lie in the description.