On the first episode cause as much mayhem as possible but do not make the Bears insane as they are needed yo call the "Fuzz". A total of 4 Cop Bears are needed for the task to be completed and as another little reward as well as the points you get a new costume.
This is the only secret Achievement on Naughty Bear and can be obtained randomly throughout the game as the Unibear shows up at any random time. You are given a warning when the mythical Bear appears with a quick shot of it skipping somewhere in the map. You have to act fast when it happens as the Unibear only shows up for a few seconds then vanishes until the next random encounter.
In the DLC trophies, the ear is not cut off. There is no reason behind this.