Crud. I joined the board after reading this thread but it ate my post because it has a link in it and I didn't have five posts yet...and then it turned out I had to wait five *days*. But no matter, I saved it.
Anyway! I notice a lot of people have suggested Pokémon characters, but here's one that may have escaped attention--Jirarudan from the second movie. Let's go through his traits, shall we?
-He's driven by his obsessions to the point of shutting out everything else around him
-He talks all the time, in very odd ways (he's almost narrating his own actions at some points), but only speaks to a human once...
-...and when he does, she's screaming at him, obviously furious, and he replies to her words alone, the tone seeming to go completely over his head
-He seems to have very little empathy or understanding of other creatures
-He has a rigid adherence to what he deems to be obvious rules and expects others to follow them to the letter (it doesn't even occur to him that letting the kids out of the cage would be a Bad Idea, because it's unthinkable to him that they would be so rude as to damage anything in his gallery...a mistake that costs him everything)
-He's disturbingly smart (we get that he's intelligent from the movie, but a sketch sheet used in production identifies him as having "frightening scientific knowledge")
-He has sensory issues (That outfit...in tropical islands...in the middle of summer...and according to that same sketch, he wears a long-sleeved shirt under it)
-He has an inability to connect with the world outside his ship (this is more obvious in his image song, but basically it comes down to that that's his world and nothing else matters to him but his collection, his ship, and his disconnection from society)
-He interprets the legend literally without considering that it may have alternate meanings (of course, he's also the only person in the film who actually *believed* the legend at all up until things started going weird, considering that the islanders said that the festival was "for the tourists" because no one really believed the story...which is kind of strange in and of itself)
Honestly, I doubt he ever put two and two together and realized that it was his own dumb fault that everything happened. Not that he's blameless, but it was beyond his intention, and he never really seemed aware of the real consequences of his actions beyond that it cost him everything he ever built (man, I can't think of that last shot of him without getting sad).
...and yes, he's my character obsession. I can go on for hours about him if need be and he got maybe 20 minutes of screen time. Which is a shame because he was fascinating.
Some people say Tracey may be autistic as well, given that he hyperfocuses, obsesses, fixates, seems to have stilted social skills, and (at least in English, haven't heard enough OI episodes in Japanese) has a very pecular speech pattern...but I'm not sure, because he also makes two very major life changes on the spur of the moment (traveling with Ash and staying in Pallet).
Cyrus also gets suspected, but if anyone was to sit down and try to diagnose that man, he'd probably wind up with a list of disorders the length of my arm. He has the flat affect (in the games anyway), the tendency to ramble on about things no one else cares about, the strict adherence to order, and the reputation for being extremely "logical" (although given what his plan WAS I'm not sure how his agents continued to call him that after it was revealed)...but he's also just plain psycho. If he *is* autistic, it's combined with a bunch of other stuff, and would probably be down near the bottom of the list.
By the way, whoever mentioned Lilo? And Izzy Izumi? I love you. Seriously.