One interesting aspect to simulations of our own universe or own brain (plus sufficient environmental context) is that there always appears to be at least one "god" from the perspective of the entities within the simulation, even if they cannot detect it. On the other hand many claim that the "real universe" definitely has no god. Does this not imply that those same people are 100% sure our universe is not a simulation?
Or, can the entities in a simulated universe eliminate the necessary existence of at least one "god" by postulating that the simulation they exist within is merely an accident of some kind - perhaps the result of enough monkeys playing with enough pebbles on a large enough beach for a fairly long time? If so, does it matter if neither the monkeys nor any other entity at that level or higher have the ability to recognise the encoding used in the pebbles-on-a-beach-accidental-simulation?
If it's something like the monkeys playing on the beach, then when does the simulation universe actually exist or change. Is it when a pebble is first placed in a "correct position", must the pebbles always be placed in some particular order?
Let's get really fanciful now, say the moneys accidentally create a pattern of rocks similar to that in the
XKCD cartoon strip but with a few errors here and there. Then along comes some "intelligent" stick figure fella who happens to be be familiar with Wolfram's rule 110. Stick figure fella recognises the pattern as being close to a production of rule 110 so (perhaps being some kind of savant) he then wanders up and down all the rows making all changes required to produce the correct pattern. Is a universe being simulated even though neither the monkeys nor the stick figure has any idea of what the encoding is or represents?