When I visit anythinghere.mysite.tld I get a DNS error. However, if you observe the behaviour of anythinghere.google.com and anythinghere.example.com you'll see there's no DNS error.
Note: doesnotexist.mysite.tld, random.mysite.tld and so on don't exist; all non-existing subdomains seem to be affected. What could be the reason for getting a DNS error in this situation?
Note 2: I'm using GitHub Pages with CloudFlare.
Update: If I clear my browser cache the DNS error doesn't happen. I see the exact same behaviour at random.lsquo.com as I see at random.google.com. That's good as it's exactly what I want. However, when I then visit lsquo.com again and then re-visit random.lsquo.com I see the DNS error again.