The one I can't forget is when I mentioned Maglor had a dog in one of my fics. Someone immediately sent me to a fic they'd written because their author note quoted a bit from Lays where after Huan left, no hound would follow Celegorm... and they'd broadened it out to mean no dog would follow any Fëanorian ever again.

Err, what?! Honestly, some people...

Incidentally, I love the idea of Maglor with a dog. Which fic of yours is that?