 SPOILER: When the Narrator is being stitched up after fight club,  the Narrator says that Tyler sometimes spoke for him. Tyler says:  "He fells down some stairs", the Narrator then says to the doctor:  "I fell down some stairs". The same happens when Marla and the  Narrator are arguing and Tyler is in the Basement saying "This  conversation is over" and the Narrator says the same to Marla.