I have a headcanon that Greece is autistic, and some of the people I know think that Belarus, Russia, and Denmark are also (possibly) on the autism spectrum. I think that Greece could be autistic because he's usually very quiet and calm, and he's pretty much obsessed with cats.
If you think anyone else in Hetalia might be autistic, please please please reply!
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"They laugh at me because I'm different; I laugh at them because they're all the same."