I always pictured you as a straight up bedwetter.
Hello, in an American movie, at a party a high school boy named Charlie Linderman comes up to two girls, Lori and Kia. Charlie's love for Lori is unrequited. He's a bit of a nerd and Kia finds him disgusting because of that.
Lori: What happened to your clothes?
Charlie: Oh, this. I was playing a drinking game with some of the lower primates and I guess I'm penalized for my ability to read above a fourth-grade level. [What actually happened to him: a bunch of guys from school tried to "drown" him in beer, force-feeding it to him."]
Kia: Linderman, you know, I always pictured you as a straight up bedwetter.
I don't understand Kia's line. What is she saying? And does her using the past tense mean she has a different opinion about Charlie now?