Bonus points if the author first mentions a specific trait, physical build, or whatever else halfway through the novel and totally fucks up my mental image.
I don't expect a biology model description for each character, but write me something brief and evocative of how they should look, you fucking dork author. I don't even know how tall she should be, her hair colour, anything. Why are you like this, author?
Whaaaaaat? You don't want a sci fi author to be like "this is Eric; he has black hair and is tall, this is his buddy Paul, he's muscular but of average height, this is Alice, she is also tall with almond eyes and has gigantic gazongas"