Disgust is one of the five emotions controlling Riley's mind and helping her. When their leader, Joy and another emotion, Sadness literally get lost in Riley's mind, she and the other emotions have to keep Riley's head on straight until Joy and Sadness get home.
Disgust is the fourth emotion after Fear, Sadness and Joy to be controlling Riley when something is unhealthy or something isn't right; throughout the film it was mostly broccoli in Disgust's case. Later on, when they move to San Francisco, they find out right away that their new home isn't like their old home, so they think that the van with their old stuff in it is coming, but they find it's not coming until next Tuesday, so they go and have lunch to forget about it, but it turns out they serve pizza with broccoli, and Disgust completely gives up on that because it seems too much for her to handle.
After Joy and Sadness got stuck in the tube where Riley's memory cores go, Disgust, Fear, and Anger have to try and keep Riley till they come back, which technically none of them are Joy, which results in them changing Riley's mood after her mom told her about a new hockey team; this however fails and leaves her and the male emotions to come to the realization that to make Riley happy without Joy. Anger soon comes to the thought of carrying out the idea of making Riley run away back to Minnesota so that she can return to her original life. Despite her skepticism (as well as Fear's protests), Anger carries out the plan, which she and Fear immediately regret.
While Riley is on the bus, about to leave from her new home, Joy and Sadness return. She intimidates Anger into erupting in flames and then she and Fear rescue the two emotions before they fall into the memory dump. Sadness then takes control of the console to get Riley to return back to her mom and dad. They go back and she gets comforted by her parents, ultimately ending the ordeal and creating a hybrid memory mixed between Joy and Sadness. Next time they went to hockey, they control Riley into aiming for a goal with the newly upgraded console, resulting in her scoring a goal. Afterwards, everything the way it was before the incident, and the emotions continue to help Riley cope with her new home.
Fear and Disgust
Disgust talking with Joy about the plans for Riley's 1st day of school
Disgust with Joy and Fear
Fear attempting to cheer Disgust up by stating what would Joy do.