My thoughts about fan-fics and oc are that thier stories take place in a different universe from the normal canon equestia, say for example, your oc name is bob, and he is a pegusus who farts rainbows, and he is married to Rainbow Dash, even if you claim it is true and it happens after the show, that's your crazy little universe with whatever things you want in it, now here are some random examples-

-equestia girls universe, which is canon, it is The same as the show, but is a humanized version.

-equestia.Mov, where the .mov series takes place and jappleack is.

-Fallout equestia-where everything from someponie's crazy fan-fic about a pony style equestia

-Noble's equestia, where rainbow factory was undecovered, and it entered a new age of power using spectra

-Rainbow factory universe, where pegusus where who failed flight test would get thier colors taken away, and killed

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And others, but if i mentioned all of them, it would take me about forever to mention everyponies insane fan-fic, which means if the multiverse theory was correct there could be a possibility of a equestia, which the multiverse theory is shown to be real to equestia by the factor of equestia girls, which shows there is a multiverse equestia, and if we, humans may get inter- multiverse travel, you may be able to see your universe you created with your crazy fan-fic, and possibly your oc, i don't mean art or something, but a living breathing, copy of your oc (i will gladly provide ice cream to share with your oc), as long as you didn't kill it off-