Which one doesn't belong?

Jacob will tell you. It's the one in the back seat with the blond hair. He asked me to hand him the girl and when asked which that was, he identified that one as the girl, and the others were not, apparently. These are like 40 year old toys that he plays with up at Camp. They are all the same, not hippy and jacked like Barbie and Ken, respectively. No long hair, wild doe-eyes and curvaceousness from head to toe like the Bratz. How did he get that this one was the girl and the others were boys?

The only differences I can see is that the 'girl' has eyelashes instead of thick 'man-brows' like this dude, and then 'she' is donning a little ruffled collar, while 'he' is wearing a tie. The blond isn't even wearing pink! Jacob couldn't tell me what it was that made him identify the one in green as a girl. So at four years old, gender stereotypes are that ingrained in his schema of the world that he can instantly identify genders but not even recognize what it is that makes him come to that conclusion...