Chase

Chase is a state of mind - When you think of someone, the right person, but you think of them in the complete opposite gender and personality. Then you realize two seconds later that you goofed up, and that they're actually the other gender and personality. This happens mostly to online friends, as you don't think of their real gender, and often role players, as you think of their character more often, and some people like role-playing as the opposite gender.

I was just in a Chase. Gosh, I thought she was a he, how bad am I at this?