Yeah, this really exists, there's a guy at work who's completely useless, makes shed loads of mistakes, never finishes the day's work load so I have to do it on a monday morning when I get back in the office, and yet somehow he got 89% on his first year uni exams?! I don't understand how someone who is obviously intelligent can be that useless!
Although I'm sure you're not that bad. He's the most extreme case of it I've come across!