This weekend we watched my boyfriend's nephew who is four years old. My daughter,who is three, was extremely excited to have him over. I loved seeing them play together, its funny to just sit back and watch the way children interact and the things that they say. Through out the weekend they did a lot of playing, with toys that are seen as the traditional "boy" and "girl" toys (trucks, dolls, action figures). But, what really caught my attention, however, was when they pretended to be superheros. On any regular day my daughter would have been Captain American, her favorite superhero, but this weekend she was Batgirl. Her cousin who is a fan of batman chose his superhero, but my daughter instead of being batman as well, said she would be BatGIRL. When I asked her about it, she said. "Because I am a girl and Batman is a boy" so then I asked her why she acts like Captain American any other day and she said, "Because he's my favorite." So I continued to ask her questions about why she prefers to be one or the other, and it basically came down to, her following her cousin's lead, since he was Batman, she was going to be his helper, Batgirl. I encouraged her to play in any way that she wanted no matter weather it was boy or girl position. From this she then continued as Batgirl, since the storyline they were playing with was of Batman and his sidekick.
There were also other instances that I overheard where gender played into their playtime. They also acted out roles of Prince and Princess and Mother and Father. My daughter doesn't usually have someone at home to play with that's her age so I'm thinking that maybe having someone there she just made her want to play the role that they wanted her to play.