There's a communal fridge at work that contains several cartons of milk, presumably so my colleagues can use it to lighten their coffee. I thought it would be amusing if I bought my own container of milk and then lurked in the coffee room, waiting for someone to appear. Then I would take a hearty swig from the carton, and when they react in horror - "How can you drink from the carton, uggghh!" I'll say "What? I've been doing this since I started here."