Na verdade, há seis cenas / flashes em que vemos Brad Pitt antes de O Narrador encontrá-lo no avião. Uma lista deles foi compilada aqui .
O raciocínio por trás disso é abordado bem em uma FAQ da IMDb :
As astute viewers will have observed, Tyler Durden appears in the film six times prior to the scene where The Narrator meets him on the plane. Four of these appearances are single-frame flashes, which director David Fincher refers to on his DVD commentary as "subliminal Brads" (a single frame is 1/24 of a second in duration, just slow enough for the human eye to register). The first subliminal Brad appears while The Narrator is standing at the photocopier at work, trying to stay awake; the second appears as the doctor (Richmond Arquette) tells The Narrator that to see what real pain is, he needs to attend the testicular cancer support group; the third as the support group leader (George Maguire) makes his opening remarks; and the fourth as The Narrator watches Marla Singer (Helena Bonham Carter) walk down an alley. Durden's fifth and sixth appearances are not single-frame flashes but cameo appearances: he is the furthest waiter on the right in the hotel welcome video and a passerby on a walkway in an airport.
On his DVD commentary track, David Fincher explains that the idea behind the subliminal Brads was to convey a sense of exasperation on the part of Tyler Durden; it is as if The Narrator has already created Tyler, but is hesitating to release him. The subliminal Brads are an attempt to illustrate Tyler's frustration with The Narrator -- if The Narrator would simply allow him free reign, Tyler could tackle many of the problems holding The Narrator back. Significantly, all four subliminal Brads appear at times of stress, as if Tyler is choosing these precise moments to remind The Narrator that a solution is within his grasp, he just needs to follow through with it.
Resposta a um comentário: Por que Tyler é como é, considere o seguinte diálogo do filme em uma conversa entre Durden e The Narrator:
Tyler Durden: You were looking for a way to change your life. You could not do this on your own. All the ways you wish you could be, that's me. I look like you wanna look, I fuck like you wanna fuck, I am smart, capable, and most importantly, I am free in all the ways that you are not.
Em outras palavras, Durden é o ideal do The Narrator, um Übermensch , uma invenção tirada das experiências deste último. , fantasias e as pessoas ao seu redor. A aparência de Durden pode muito bem ser semelhante a alguém real (ou poderia ser modelada em um ator como o próprio Brad Pitt, que alguns considerariam um ideal).