This troper had a perfect variety of this pulled on him and his entire group once by his Exalted Storyteller (GM). We were playing through the First Age incarnations of our own Solar characters, and I was pleased to learn that Justice-Bringer was a fair and just ruler of a mighty city, dispensing justice, giving out boons and generally acting like a heroic nice person. Naturally, everyone assumes that such a person must obviously be male, like most of our characters and also our entire gaming group. The twist comes at the end of the story, when Justice-Bringer is forced to flee a ball attacked by the Dragon-Blooded during the Usurpation, and then to enter a duel to the death on top of a tower wearing only a ball gown. "...Wait, you mean ball _robes_?" To which the reply was "No, I mean ball ''gown''... because Justice-Bringer is a woman. Didn't I tell you?" (And no, he didn't tell us, which also makes it a perfect example of MostGamersAreMale, ViewerGenderConfusion and possibly even SamusIsAGirl. At which this troper reflexively went
"OMG, what a clever Tomato Surprise!", to confused and worried stares from the other group members.