In the first training attempt with Apollo, Rocky is running with Apollo on the beach. Rocky is having flashbacks to his first fight with Clubber when he was knocked out early in the second round. In that fight Rocky wore black and gold trunks and in the second fight with Clubber he wore the red, white, and blue trunks Apollo gave him. While having his flashbacks you can notice Clubber give Rocky a lower body uppercut and Rocky jump in the air. He is wearing the trunks he wore in the second fight rather than the first fight.

Editor's Note: This is really similar to another slip-up, but the other has it in a different scene.