The Decoy Monkey is a fake monkey made out of rubber. When a Bloon within its range uses an attack, there's a 50% chance that it will attack the Decoy Monkey instead of the tower it would otherwise attack. The Decoy Monkey has 50HP, and many upgrades which improve health and other things. If a Bloon is within the range of multiple Decoy Monkeys and ends up attacking a Decoy instead of another tower, it will target a random Decoy. It would look similar to a Dart Monkey, but well...rubbery I guess.