The Smallville Clark Kent meets his version of Oliver Queen in Season 6. The success of this Oliver led to Arrow even though they are different continuities. The Smallville Oliver founds the Justice League although the Golden Age Green Arrow was in the Seven Soldiers of Victory and the Silver Age Green Arrow was not a founding member of the Justice League but an early recruit to it. I think that the third cinema Batman is destined to found the cinematic Justice League. He will tell Amanda Waller, "You back off - we are forming a team!"
There are metafictional relationships between continuities and sometimes they coexist in a multiverse. The Superman film theme music is heard when Christopher Reeve plays Virgil Swann in Smallville. We are explicitly reminded that Reeve played Superman in an earlier screen adaptation of Siegel's and Shuster's original comic strip. I started reading Superman, Batman and Green Arrow in the 1950s, less than twenty years after their creations.
How many continuities have I referenced here? Not the full list.