Hats are transferrable across sites! You read that correctly: this year, if you earn a hat on any site, you can wear it on any participating Stack Exchange site. This was one of our most asked-for feature requests after last year’s event, and it’s a great way for everyone to highlight their achievements on their favorite site across the network.
With this in mind, why it is not also possible to earn some hats by completing requirements across multiple sites? For instace, getting at least 3 answer with 5+ score? I would feel horrible to make up 10 questions just to earn Mr. Binx hat on SO. Althought, I asked few questions here and some on other sites.