The enemies of the series are "Bloons". (The trademarked word Bloons is a spinoff of the word ""balloons"".) Once the Bloons come, a monkey will have to be placed to pop them. These monkeys pop the bloons. Red Bloons release no "children". B.A.Ds also have no "parents". Children & parents are terms determining what Bloons release when pop (children) and what Bloon releases that Bloon (parents). For example, the child of a Blue Bloon is a Red Bloon, and the parent of a Blue Bloon is a Green Bloon. A Red Bloon Equivalent (RBE) value is the number of Red Bloons it is equivalent to.