Coop is a character and minor former villain seen with some of the other villains in the Yin Yang Yo! intro in Season 1.
He is a nerdy chicken who appears to be scared of any threats and has a huge crush on Yin. But because she never returned any of his feelings, Coop joined the Night Master in exchange for the promise to have Yin when the world was taken over. Coop gave the impression of incompetence, but in reality, he had powers and abilities rivaling Yin and Yang's. In the end, however, Coop couldn't bring himself to go through with the Night Master's plans and held him in place so Yin and Yang could destroy him. However, like the Night Master, Coop disappeared as well, but returns in the "The Pecking Order", stripped of his Night Master energy that spread across the world, possessing all who ingest it until Coop absorbs a large amount of controlled evil, enough to make him a Night Master.