Christopher Reeve and Adam West are coming back to don their respective capes in the 'Flash' movie -- that is, if you believe would-be leaks ... which have the DC internet ablaze.

Rumors have been lying this week about supposed cameos that both Reeve and West -- who, of course, are deceased -- allegedly have in the new WB offering ... which is now slated to come out next summer after a lot of shuffling around lately.

According to lionized movie leakers -- some of whom have solid reps for being in the know on this comic book-flick stuff -- the word is ... CR and AW are going to be featured in a scene where Barry Allen (The Flash) is hopscotching around different superhero universes.

Apparently, you only see them briefly ... and the Flash character doesn't interact with them either, but rather ... sees them in action in their own worlds/timelines.

The rumored cameos are said to be from old archived footage -- so, no, they're not making all new content/dialogue/scenes with these late actors via deep fake CGI ... or so it seems. Oh, and they're not the only DC OGs popping up apparently ... Lynda Carter as Wonder Woman is expected to also cameo in her prime as well -- at least according to these folks.

Different cuts of the film have been screened a handful of times now -- it's in the can at this point -- so take all this with a grain of salt ... Warner could majorly switch things up by 2023.

There's also the question of what this movie and all its implications might mean for the DCEU long-term. Beyond Ezra Miller's controversies, there've been reports Discovery honchos might want to overhaul the entire superhero strategy going forward now that they own it.

With all that in mind ... we wouldn't recommend getting too excited about any of the plotlines, character teases or mixing and matching of universes that might arise from this movie when it does release -- i.e. Michael Keaton's reprisal, or a potential Cavill return, etc.

Sounds like there's no clear vision yet as the new Warner Bros. Discovery gets started here ... so any or all of this could be scrapped or rebooted entirely -- and it may be all for naught.