Donnie got infected by the Kraang but he hid it from the others for a while, but eventually his brothers found out so they locked him in a glass cage. He still has a bit of control left in him, but the infection made him a carnivore. And he has a thing called a hive mind that takes over when he gets hungry, and the infection causes him to say and do things he can’t control. The hive mind often makes him say things that are cruel and teasing. It often tries to lure people to let him out the cage.