Exploding Darts

When Exploding Darts is bought, darts from Dart Monkeys (not Monkey Aces or Super Monkeys) explode when the maximum amount of bloons are popped. This can pop lead bloons and costs 7. It disappears when upgraded to a Spike-O-Pult. A player can technically finish a BTD4 level with Exploding Dart Monkeys all over the screen. However, the downside to this defense are the Camo Bloons. In BTD5 the upgrade is called Splodey Darts and it allows the Spike-O-Pult and Juggernaut to explode as well!

Trivia

 * It is easily possible to beat any map and mode with this upgrade on.