Anyone who played Nier Automata to completion (and possibly played previous tittles) knows that multiversal dimension hopping is built into its lore, so its not really far-fetched that something turned up on our side.

For the FF14 side, I will reserve judgment until we see the full story. For me Ivalice was more out of place in an uncanny valley kind of way: not quite apart from the world, but not quite integrated either, retaining its Tactics taste (which admittedly I'm not a fan of).

Regarding the Regalia... the visuals are somewhat out of place, but as far as function goes, its nothing that in world allagan or magitek technology cant achieve. And the visuals are rather easy to swallow, given the amount of half naked buff roes I see running around with chicken heads.