- Arthur McFly: "Hey! You can't treat her like that!"
- Sully: "Oh yeah? Says who?"
- Arthur McFly: "Says me!"
- — Arthur McFly stands up to Sully for pushing Trixie Trotter to the ground.
Sully was a member of Irving "Kid" Tannen's gang. When Kid Tannen apprehended Marty McFly, who was going by the name "Don Corleone", and Arthur McFly, Kid was interrupted by Sully. Sully told Kid that dynamite at the warehouse on 4th Street, and that he caught the arsonist who burned down the old speakeasy.
Kid Tannen left Sully to keep an eye on McFly, "Corleone", and Trixie Trotter, since he wanted to deal with them personally. Trixie Trotter tried to beg Sully to let them go, but he pushed her to the ground. Arthur hit Sully, and knocked him out with one punch, to Trixie's amazement, just as his son would do to protect the woman he loved 24 years later.