In the comics it was Batman's enemy Ra's al Ghul that got ahold of Batman's secret files regarding his Justice League teammates and their weaknesses instead of Vandal Savage.
Phil Morris reprises the role of Vandal Savage from Justice League (2001). Morris also played John Jones aka The Martian Manhunter on the television series Smallville (2001).
Kevin Conroy (Batman), Tim Daly (Superman), Susan Eisenberg (Wonder Woman), Carl Lumbly (Martian Manhunter), Phil Morris, Olivia d'Abo (Star Sapphire), and Alexis Denisof all reprise their previous television roles for this film. Additionally, Michael Rosenbaum, who previously voiced Flash Wally West, returns to voice Flash Barry Allen.
For the Justice League members that appeared in both the original comic storyline and the film, the contingency plans that Batman developed differ between each version. A few examples from the comics are that Superman was exposed to a special red kryptonite that caused his skin to turn red as a result of absorbing too much yellow solar radiation or that Green Lantern's ring caused him to go blind due to a post-hypnotic suggestion that made him believe he was blind which was placed while he was sleeping. In the film Superman was shot with a Kryptonite bullet, and Green Lantern was made to doubt the powers of his ring by giving into fear.