The first man in the movie is Dom, although he doesn't immediately speak. The first person with lines is one of Saito's projections, which immediately raises the question: Do projections count as people for the purposes of the Bechdel test? They're certainly characters in the movie, but they're only real within the dream. My first instinct is to say that projections should only count when they reflect real people; for example, Dom's projection of Mal, and Fischer's projection of his dying father. However, I think it would be more interesting to keep track of both reality and projections, so that's what I'll do.
What if only real people count?
(I am assuming for simplicity that people who seem to be real actually are.)
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What if projections count too?
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Ariadne: "My name's..."
Mal: "I know who you are. What are you doing here?"
Ariadne: "I'm just trying to understand."
Mal: "How could you understand? Do you know what it is to be a lover? To be half of a whole?"
Ariadne: "No."
Mal: "I'll tell you a riddle. You're waiting for a train, a train that will take you far away. You know where you hope this train will take you, but you don't know for sure. But it doesn't matter. How can it not matter to you where that train will take you?"
It could be debated whether this conversation passes OB-3. Aside from the issue that Mal is actually Dom (at least, his subconscious), it could be argued that Mal's lines about being a lover and about the riddle are about a man, to the extent that they are about her relationship with Dom. In asking what Ariadne is doing "here", Mal is also in effect asking what Ariadne is doing in Dom's dream. However, I think this is reading too much into it. "What are you doing here?" is a straightforward question. Although the line about being a lover is clearly about Dom and Mal together, the riddle is different. By telling Ariadne the riddle, Mal is trying to tell her about her own history. This is Mal's way of introducing herself. I believe that this scene counts, and Inception passes OB-3.
Conclusion
Inception is without question male-dominated. Of the six members of Dom's team, five are men. Ariadne is the only woman. Of course, if incarceration rates are anything to judge by, a five-to-one male:female ratio on a team assembled for an illegal job is higher than normal-- only 8.8% of prisoners in the United States are female (Arthur lives in the US, and Dom is trying to get back). That number is 3.7% in France (where Ariadne is from), 4.5% in Kenya (where Yusuf and Eames are working), 7.0% in Japan (where Saito is from) and 7.2% in Australia (where the plane leaves from, and presumably where Fischer lives). Ariadne's inclusion in the six-person team makes it 16.7% female.
Even so, there are only six female characters in the movie, as noted above, and one of them is a man in disguise. There are only two with any significant on-screen presence, and one of them is the movie's antagonist. Ariadne is said to be a better architect than Dom, but her purpose in the movie is to probe Dom's mind and find out why his subconscious is manifesting Mal in his dreams.
So what about that final scene? Different interpretations of the final scene could color the results of the Bechdel test. On the one hand, it could mean that every single character except for Dom is a projection; or maybe there are other real people within the dream, but some that we think are real are actually projections, and maybe some that we think are projections are actually real. On the other hand, if he is in the real world in the last scene, then the distinction between real and projection would follow the same lines that I've drawn in the sections above.
Ultimately, the final scene is the reason why I think the Bechdel test should include both real and dream characters. The movie is intentionally ambiguous as to the nature of reality here. To draw a definite distinction between "real" and dream characters for the Bechdel test presumes a certain interpretation of the final scene, and I don't think its appropriate to do that. It is better to interpret the Bechdel test with regards to film characters rather than "real" or "not real" people within the film, and leave the interpretation of the film itself to the viewer.
Since projections count for this reason, Inception passes both the Original Bechdel and Reverse Bechdel tests.