I am VERY good at making up answers to questions that I don't know the answer to. I do it for the sole purpose of seeing if people will believe me and I usually explain the whole logic of my answer to ensure the believe me. But if it is made up I ALWAYS tell the person after that I was making it up, usually ending with a comment like "but it sounded right huh?"
On the same note, I am also really good at telling when people are making up there own stories and will almost always call bs.