Never say any of the following things to your students:

• 'I have your final exam right here in my pants.'
• 'Mmph mmph hglughlugh oh sorry I thought you were a letterbox.'
• 'Good question! We should talk more about this. Why don't we step into my orifice?'
• 'I swear to Christ I'm going to kill you and everyone you've ever met.'

Now find me a new sofa.