I hate

Fan theories, or more specifically the kind of fandom that constantly tries to guess what’s going to happen when a trailer comes out, or that tries to somehow “solve” certain plot points with elaborate constructions.

I like plenty of juvenile stuff some would consider way below my "acceptable age range" but when I see anyone use words like "headcannon" in a serious context all I see in my minds eye is a 4 year old playing with toys with their imaginary friend.