Who wants to play soccer? It's just kicking a ball and pretending to be hurt! 
Soccer Trolls are creatures that the Teen Titans find encased in their soccer ball. These trolls debuted in Kicking a Ball and Pretending to Be Hurt.
Biography
The Teen Titans, enlivened by the game of soccer, are all pumped up about the game. Robin is holding his "stylish" soccer ball in the air for glorious purposes, but the other Titans gasp: no using hands in soccer! Robin drops the ball immediately, and it cracks open in a brilliant flash. Inside awaits a Soccer Troll who frightens all of them. He explains that he, along with numerous other Soccer Trolls, are packaged in soccer balls, which somehow magically makes people enjoy soccer. Robin is outraged with this, and he demands that the Soccer Troll takes him to his leader.
The Soccer Troll leads them to an underground kingdom ruled by King Goal, the ruler of all Soccer Trolls. His realm is a huge soccer arena filled with Soccer Troll fans to the brim. After the Titans defeat (well, sort of) King Goal, all of the Soccer Trolls refrain from being enclosed in soccer balls anymore.