At the prom, when Mandela comes up to Kat asking her where William is. Kat replies, "Oh Mandela, please tell me you haven't progressed to full on hallucinations." Then Patrick points to Michael. Mandela waves at him. Then they show Michael up on the stage. Then they show Mandela smiling. When Mandela is smiling, you see in the background (on the left) Kat and Patrick spinning off dancing. Then they show Michael coming through the people to Mandela. While they show him coming to her, you see the back of Kat's head. (almost in the middle of the screen) I thought she was off dancing with Patrick?! I know for sure it couldn't have been a time lapse because the song was never interrupted.

Editor's Note: While filming a scene with music, there is actually no music playing. The music is added in after production. So this slip-up could be valid or false. You decide.