Joy is the protagonist of Inside Out. She is the yellow Emotion and the main Emotion out of the five that live inside the mind of Riley, the others being Fear, Anger, Disgust and Sadness. She appears to be happy all the time and full of energy.
Amy Poehler describes her as follows: "Joy is the engine. She keeps everyone moving and happy. She represents the parts of Riley that are starting to change and become more complicated, and she is reluctant to let that change happen. She may be the most positive, but in many ways, she is the least flexible."[1]