They are always fanon. The internet has a fascination for producing gender swapping regardless of the context of the canon character. Closely related to Gender Bending. Crossdressers, of course, provide their own version of this. There's a good chance that you'll see the character in question in a more gendered appropriate outfit (i.e. pants become a skirt, necklines are lowered, etc.). One of the Rules of the Internet. It can (and often does) overlap with Rule 34.