I used to charade as a girl several years ago. It was when I started playing Star Wars Galaxies, an MMORPG. I had just come off playing a game and frequenting a forum that made me start to feel insecure about my manhood. I chose a female character for the fun of it, and though it would be interesting to try.
As I got into it, I found the female persona to be interesting to roleplay. I told people I was a girl IRL, became fascinated with cosmetics and clothing in the game which further "proved" I was a female to the men I played with. I met 2 guys I played with a ton, and one of them developed a serious crush on me, which I just shrugged off and didn't let go further because I wanted to keep my identity.
The other became my best friend, and we played for a while, until he decided to ditch me for World of Warcraft. I moved on to WoW with another person, played a month, then left and found that guy that ditched me in his clan, which I joined. I told everyone there I was a girl, and claimed to have no mic in vent. I just enjoyed being more feminine.
After a while, I decided it was time to let the cat out of the bag to my guild. I made a long post, apologizing to my best friend and the guild. Half of them knew I was a guy, and the other half were surprised. I just kept playing with them for a while until I quit. I haven't done something like that since.
To me, everyone on the internet is male until proven innocent.