From the rumored list of kids who were up for roles in George Miller’s live action JL flick, Adam Brody always made the most sense. From what we know of the script, the Flash that fills out the majority of the movies screen time is Wally West’s flash, and there are definite arguments for similarities between Brody and West.
From the article; Brody, best known as the heartthrob on "The O.C.," joins Australian supermodel Megan Gale, who was reportedly cast as Wonder Woman, apparently beating out Jessica Biel for the part.
Among the other young actors rumored to have been cast are "Friday Night Lights"' Scott Porter as Superman and "Wolf Creek's" Teresa Palmer as Talia al Ghul -- a recurring love interest for Batman. Common was rumored to be playing the Green Lantern (a.k.a. John Stewart).
I haven’t seen the news for Scott Porter or Teresa Palmer portraying those roles, so that’s news for me too. But as for Megan gale “beating out Jessica Bile for the part”: entirely fabricated. Jessica Biel was only rumored to be up for the part, before her management denounced the rumors.