It's unlikely that the writers who created these characters consciously decided they would give them an undiagnosed mental disorder as one of their traits. Maybe they were just borrowing behaviors of a "quirky" friend, or maybe the writers suffered from the disorder and wrote the characters to mimic their own life.
But one way or another, these characters show all the symptoms ...
6Sherlock Holmes -- Asperger's Syndrome
It's tough to pin down the exact personality traits of Sherlock Holmes, since his story has been recycled in so many incarnations. He's the most-portrayed fictional character in the world, running the gamut from Basil Rathbone playing a jolly English gentleman who fights Nazis to Robert Downey Jr.'s Victorian Rain Man/MMA fighter. But there are some key characteristics in the original Arthur Conan Doyle version that tend to crop up again and again, and they all indicate a severe case of Asperger's.
"Solving crimes is all well and good, Watson, but I have a Yu-Gi-Oh! forum to moderate!"
The Red Flags
Before you skip down to the comments to submit your passionate defense of Holmes' mental state, we're not the only ones who think he shows up on the autism spectrum. Holmes' hyper-keen observational skills, social mannerisms and overall personality have fueled Asperger's rumors everywhere from Holmes fan forums to Asperger's support forums.
"Holmes, stop looking through my stuff for clues. This is the reason no one else will lodge with you."
The first thing to keep in mind is that the character isn't just portrayed as being really smart -- he is obsessed with certain subjects and totally excludes all others. In one of the Holmes stories, A Study in Scarlet, he doesn't know that the Earth revolves around the sun (because, he says, the information doesn't have any effect on his everyday life). These uneven obsessions with random topics -- in Holmes' case, things like tobacco ashes and regional soil consistency -- are not signs of an enthusiast; they are symptoms of a disorder. Or, as the Yale Child Study Center puts it, Asperger's sufferers show "...a narrow range of capacities for memorizing lists or trivial information, calendar calculation, visual-spatial skills such as drawing, or musical skills involving a perfect pitch or playing a piece of music after hearing it only once."
"Care for a 70th rendition of 'Baa Baa Black Sheep,' my dear Watson?"
And most telling is that Holmes' talents are coupled with an inability to interact socially with anyone but Watson. He embarks on long-winded monologues about very specific topics, oblivious to the listener's lack of interest. If you know someone with Asperger's, you're well familiar with this habit.
It's true that the disorder wouldn't be recognized until 70 years after Doyle invented the character. But obviously the disorder existed long before there was a name for it, and Doyle didn't have to know what the disorder was called in order to have known somebody with those quirks, and written them into his fictional detective. Perhaps 70 years from now, experts will have a name for the ability to slow down time and punch people in slow motion.