For a while I never understood how a wrong passenger gets through boarding pass check. At DFW on time, I saw an example of how someone can slip through the cracks. A non-English speaker was brought to the gate by an airport agent and told to wait for the NEXT flight. She tried to board the flight I was on instead. Boarding pass wouldn't scan OK, so one GA sent her to the GA at the counter. The GA at the counter talked to her and then yelled out "She doesn't speak English, just let her on." At this point a couple of us who overheard the instructions of the airport agent told the GAs that she's supposed to be on the next plane... Close call.