When William tells his friends "You are not all the same" someone answers "I am" which is an opposite reference to what Brian says to the crowd: "You are all different". The crowd agrees simultaneously but one man answers: "I'm not"
When William is exposed to a grooming attemt he answers: "I will (strip) if you eat your own brain with a nice Chianti", also a reference to "Hannibal", where Hannibal Lector eats from a conscious man's brain.