Lisa and Janey are fed up of you leaving the place a state, leaving dirty washing up in soak and generally being sloppy and messy around the flat. They are going to teach you a lesson and make you get a taste of your own medicine by making you very dirty and messy, just like how you leave the flat. In fact, they are going to smother you in custard pies so you really begin to understand what dirty and mucky is like.