Sadness is the deuteragonist of Inside Out. She is the blue Emotion and one of the five Emotions inside the mind of Riley, along with Joy, Fear, Anger, and Disgust.
According to an interview with Phyllis Smith, Sadness is the voice of reason: when Joy has an idea, she’ll try and drag her down. She appears to be depressive most of the time, but there are a few instances where she is seen smiling. “None of the other Emotions really understand what Sadness’ role is. Sadness would love to be more optimistic and helpful in keeping Riley happy, but she finds it so hard to be positive. Sometimes it seems like the best thing to do is just lie on the floor and have a good cry.”