The Flash is part of the DC Extended Universe, but is it Barry Allen or Wally West?
Ezra Miller of "The Perks of Being A Wallflower" fame was a surprise and controversial choice to play The Flash. Fans were already enamored with the Barry Allen Flash played by Grant Gustin but it has been repeatedly clarified that the DC Extended Universe is not connected with the CW/TV Universe featured in "Arrow" and "The Flash."
It has been rumored that The Flash will appear in at least a cameo scene in "Batman V Superman: Dawn Of Justice." This was claimed by The Daily Superhero citing an insider.
"The scene is indeed a robbery and security cameras inside the store were used for the scene. During the convenient store robbery a sudden 'flash of wind' is seen in the security camera footage and revealed to me as being a cameo tease for the Flash."
The site also stated that there would be arguments that it could be Superman (who is faster than a speeding bullet) but it was specifically mentioned that the scene shot involved The Flash.
Now, there are different versions of The Flash but the two most popular are Barry Allen and Wally West. While there is no obligation for Warner Bros. to recognize Grant Gustin as Barry Allen and they could use him in the movie, What Culture believes they'll go with Wally West.
"Seeing as Batman has been operating for years, who's to say that Barry Allen couldn't have been doing the same, only to have fallen in battle years earlier, passing the mantle on to Wally as he did in the comic books?"
Again, the timeline of the DC Extended Universe is unique, where Batman is older than Superman. They could also play around with that concept with The Flash. Going with Wally West assures the fans will not be confused, or at least pay respect to the TV version which has been rating very well.