This happened when Long Duck Dong is dancing in the gym with the gym teacher and he is leaning on her shoulder, blowing his nose. Watch after he gets done blowing his nose. There is a string of snot dangling from his cheek. Totally gross. They should have noticed and had him wipe it off. Not a scene to watch while eating! It might not be a slip up per say, but definelty an intersting scene to watch for!