Continuities

Core series

Novel trilogy

Fazbear frights

Film series

I’m 100% sure that FNAF WORLD is non-canon but since UCN is canon and has Dee Dee and OMC from FNAF WORLD I would say that both characters came from another universe to the main FNAF universe. Since in the Princess Quest mini game we see an old man witch is theorized to be Old Man Consequences (witch probably most likely is) it can be assumed that OMC has some type of power to cross multiple dimensions and universes (possibly the same with Dee Dee). So this would mean that OMC comes from the FNAF WORLD universe same with Dee Dee and that they have the power to cross the Multiverse (or Omniverse because of the crossovers with FNAF witch are from separate multiverses such as DbD, that’s if OMC were a character in that future crossover). Take the DJMAX series for example, some characters from their spinoffs have came across the mainline story universe of their game witch could be the same case for FNAF where OMC and Dee Dee who come from the FNAF WORLD universe enter the mainline story universe. As for the reason why OMC and Dee Dee have came to the mainline story universe is unknown but it could be suggested that OMC knows something about Fazbear Entertainment and wants to put an end to it by warning the characters there, as for Dee Dee it just seems like they are there to cause trouble other than to warn or fix the mainline story universe.I highly believe that this could be true or not but it’s my theory.