Canon

For all intents and purposes, the canon of something refers to the continuity the object comes from, including other characters, premises, settings, events and concepts.

's Influence
After, whether a canon was official or not became irrelevant as it did not restrict who can be brought into. As long as the canon existed, it was fair game. Doomsday brought only one canonical version of each character, object and location, known as The Unique Clause, causing many canonical mismatches between characters that were pulled through from different canons. An example includes and  who have an equivalent of the other person in their own canon but come from two different canons,  and, respectively.

s
s, a firearm concept originally created by who has, have the unique ability to send s back to their own world and bring in a replacement in the form of another canonical form of the newcomer.