[@BCTheEntity]

To be fair, in theory just about any given anime, rpg or franchise can be present in one form or another could be found in the Warhammer 40k Universe if anyone put their mind to it. This one however makes a great deal of sense...

My personal favorite one that I've come up with myself is the idea that the Naruto world is somewhere in the Warhammer universe. I won't spoil it because a lot of the evidence revels quite a few plot twists, but things start making a great deal of sense if you consider the 'Ten Tails' to be a Demon Prince of insane power.