WARNING: The following contains spoilers for Reign of the Supermen, available on DC Universe and for digital download.
The DC Animated Universe follows up its Death of Superman by adapting the Reign of the Supermen, stitching together various DC titles of the '90s to illustrate how the Last Son of Krypton would return to action after four replacement Supermen tried to do his job in the interim.
As expected, quite a few changes are made from the source material, not just to fit the 90-minute runtime of the film, but to also match the continuity established by the DCAU. With that said, let's look at some of the deviations made and compare them to the original story.
CYBORG SUPERMAN'S PURPOSE
The source material depicted Hank Henshaw, Cyborg Supeman, as an astronaut who merged with LexCorp's technology following a meteorite accident -- the only way his consciousness could be preserved. Heartbroken about the loss of his crew and wife, Terri, Hank left Earth to explore alien culture. Isolated in the dark recesses of space, he grew vengeful, blaming his agony on Superman, which led to him co-opt Superman's arrival ship to build a new body and become the Cyborg Superman.
This movie, though, changes his background drastically, as it's Darkseid who plucks Hank from the accident. In the film, the ruler of Apokolips rebuilds Hank and sends him to infiltrate and win public favor on Earth. Hank was nothing more than a conduit to convert humans into a new legion for Darkseid, maroon the Justice League at the edge of the universe and to open a huge portal inviting Apokolips' armies back. There is no alliance with Mongol and his Warworld, no destruction of Coast City and no plot to frame the other Supermen, like the comics. Hank is merely Darkseid's lackey, brainwashed by the Anti-Life Equation.
THE RISE OF THE SUPERBOY
In the comics, Superboy was created by CADMUS' head Paul Westfield using his own DNA. But contrary to what the boy thought, he wasn't a clone at all. He was actually genetically engineered to be as Kryptonian as possible, using research Westfield did on Superman's biological makeup. Westfield's team was able to discover a telekinetic field for a human that would give them the ability to simulate Superman's powers, such as flight, invulnerability and strength, which led to Superboy -- their 13th trial -- coming to fruition.
Reign of the Supermen pulls an arc from Smallville and, most notably, Young Justice, as Superboy really is a half-human, half-Kryptonian hybrid in the adaptation. Lex Luthor uses Superman's DNA from the battle with Doomsday and splices in his own genetics to create the aspiring hero. Here, rather than Westfield at the helm, Dabney Donovan is Lex's cloning expert. Also, as opposed to trying to get Superboy to become his tool alongside Supergirl, like in the books, in this story Lex simply wants Superboy to impress the United States President so that he can be endorsed as the new Superman, giving Lex even more ins with the government.