Dallas, Georgia is where they film the town of Blue Valley, Nebraska.
Blackbriar Thorn is mentioned as having been a member of the Injustice Society of America until Green Lantern destroyed him in 1988. In the comics, Blackbriar Thorn is a druid and an enemy of the Justice Society of America. Though he spent the majority of is time in Gotham before joining the ISA and directing his anger towards Green Lantern.
Gentleman Ghost is mentioned as having been a member of the Injustice Society of America until his defeat. In the comics, Gentleman Ghost is a 19th-century gentleman thief and a member of the ISA.
Baron Blitzkrieg is mentioned as having been a member of the Injustice Society of America until his defeat. In the comics, Baron Blitzkrieg is a Nazi super-villain who later joined Lex Luthor's team of super-villains.
The little boy in the opening flashback calls himself "Bruce", Bruce Gordon was the name of the DC character who was a leading scientist in the field of Solar Radiation and was the favorite host of the villain Eclipso!