Just because someone isn't like everybody else i.e. ''normal'' (or what society defines as normal, I myself see being normal something to avoid) doesn't mean they have some mental problems. Thats the problem today too many parents and so called professionals want to blame some ''bad'' mental reason for someones behaviour and box them off into some group, just like people have done to Sheldon. Liking a place to be clean or organised is not a symptom of OCD, you just don't like living in a mess. Having a certain place you seat is not some mental problem, he points out quite clear why its the best seat for him, not liking change is no mental problem and most of the time Sheldon is right in not wanting change e.g. changing contrast levels (it takes me ages to get the tv colour just right when I first get one and its very annoying if someone changes it), and sometimes his wrong however most of the times his wrong he points it out after and corrects himself. I'm not denying he has some problems however so does everyone else e.g. alot of men (properly most depending on age) will do anything at the chance of having sex (e.g Leonard gives up the LOTR ring to have sex with his girlfriend
Its his GF they've already had sex and will again), that to me is very irrational and stupid, yet is generally accepted as normal behaviour.
As the above poster points out the creators had no intention of making a character with AS or other syndromes. Their intention was obviously to make a funny character by first making him a typical ''nerd/geek'' and secondly making him stand out from the other geeks in the show.
He is purely Sheldon.
If Sheldon really has mental problems then I should get myself checked out as his the guy I most relate to in the show.