Originally Posted by
Bored at 3:00AM
Due to Dr. Manhattan's tinkering, all of DCU history is currently in a state of flux and has been since Flashpoint. The return of Wally West at the start of Rebirth started changing history back and Superman Reborn changed it further. In other words, stories that previously never happened, happened again, people who were dead are alive again, memories are fuzzy, the Microverse is beseiged by time storms, and Power Girl has been trapped between Earths. Essentially, time is broken in the DCU right now.
So, yeah, Superman has met Ultraman a bunch of times already because history now includes all the prior battles between the JLA and the Crime Syndicate, rather than a series of "first meetings".