I feel like a fitting sub-topic to slide into this conversation is the presence of alternative fanons to canon material. Sort of alternate time-line/universe concepts that are within the same realm as the source material, but divergent enough that it evades the stickiness of rigidly conforming to an established canon. This of course falls into a world of argument where these AU universes may not be totally complimentary to the source.

My only major experience in this sort of topic is the world of My Small Technicolor Horses: Platonic Campanionship is Witchcraft and "Fallout: Equestria" so my opinion may not be all that diverse as it stands. And even then the relationship of MLP to Fo:E is something that shouldn't exist but somehow it does; and may not be compatible with other shows since the formula for that is such a impossibility. It's an anomaly in a way.

But as Fo:E stands it's one of the more successful sub-genres of horse enthusiasm spawning from its original fic a plethora of side-fics each with its own interpretation of the "canon" laid out by Kkat and all independent of each other. It's perhaps a useful model to look at when approaching existing media and its canon and to apply one's own fanon: finding a point where you can diverge from the existing canon to create something independent but related while feeding off the same image of the source material.

There is then of course the topic of juxtiposed literary ironies and opposites in FoE versus MLP, but that's a whole other topic that begins to bleed into more autism than I already laid out.