It occurred to me that an ancient gold-clad super-psyker ruler might draw particular interest from a Thorian Inquisitor, especially considering that she speaks Gothic and rules a population that uses old Terran technology and designs, on a planet largely populated by sapient, talking versions creatures that were either extant on ancient Terra, or present in ancient Terran myth. There's also the unusually large concentration of psykers and their seemingly innate resistance to Chaos corruption to consider.
It seems unlikely that Celestia is a proper Sensei, as that would require the Emperor to have gotten busy with an equine at some point, but it does seem to me like she may well have some sort of connection to him, perhaps something to do with the Star Child heresy, given the value she places on interpersonal relationships.
Thoughts?

7000625
The God Empress of Ponykind....and, you never know. If BIg E was ever a Celtic ruler, who worshipped Epona, then je would have had to stick his dick in a horse

7000628
He could have gotten really, really, really, really, reallllllllllly drunk.

7000632
I mean, Emps was kind of a light weight, at least against Leman

7000637
That's kinda like saying elephants are light when compared to blue whales. It's true, but not particularly useful as far as comparisons go.

Well, it is said the False Emperor didn't had really a defined look, it depended on his whims and partially in the perception you may have of him.... being the MOST poweful (or was, as he'just a dissecated corpse) and shapeshifting being a thing.... you get the idea

The answer to this would dwell in whether or not Celestia in the Age of Irons was born as she was or if she ascended like Twilight.

If she was born that way, perhaps some part of the Emperor got cut away during his 24/7 battle with the rest of the Warp; and maybe it managed to not get eaten by a Daemon and instead managed some form of flawed reincarnation in which its powers were passed but its memories beyond vague things like “Chaos Bad” were unable to

If she ascended, then it probably lies in whatever makes the planet so strange in the first place. Maybe the Emperor visited the world at some point and left something there, either as a gift or experiment, than is responsible for things like the Alicorn ascension and for all the human tech and language

7000628
Confirmed. The Emperor is responsible for all the Zeus slept with an X myths or Zeus transformed into an X and impregnated someone.

7000716
Arguably, her extreme distaste for Chaos but willingness to tolerate it due to great need is itself another reflection of the Emperor. If I recall correctly, there are implications that some of his accomplishments were managed with the assistance of the Dark Gods, part of a bargain that was broken, although by I'm not sure by whom.