The Clown & the Bat

The Clown & the Bat is an easter egg found in the map First Contact. To obtain it, one must complete the Ladder. In the Reception room, one can see who appears to be Batman out the front. Shooting him will cause him to disapear. Returning to the first floor, one can find a set of Joker Teeth. Shootign them will trigger the sound of the Joker laughing. Return to the reception room, and you will see Batman & The Joker battling outside. Shooting Joker will give you The Bat Perma-Perk, which slightly increseases defense, whereas shooting Batman (who can only be killed with a headshot) will give the Last Laugh Perm-Perk, which drops a Joker Bomb every time you are downed.