Atom [Ryan Choi]; Justice League [JLA; Batman [Bruce Wayne]; Green Lantern [Hal Jordan]; Hawkgirl [Kendra Saunders]; Superman [Clark Kent; Kal-El]; Wonder Woman [Diana]] (cameo); Mr. Choi (Ryan Choi's dad; flashback); Dean Mayland; Panda [Dr. Potter]; Professor Helmond Kettering; Dr. Thomas Dinawa; Dr. Martin Campbell; Dr. Edwin Katz (dies); Praetor (villain); Sergeant Slak (villain)
Atom [Ryan Choi]; Dr. Panda Potter; Professor Helmond Kettering; Dr. Thomas Dinawa; Dr. Martin Campbell; Amanda; Praetor (villain); Sylbert Rundine [Dwarfstar] (villain, introduction); M'nagalah (villain)
Atom [Ryan Choi]; Dr. Panda Potter; Professor Helmond Kettering; Ms. Turner; Dwarfstar [first appearance in costume; Sylbert Rundine] (villain); M'nagalah (villain); Giganta [Professor Zuel] (villain)
Atom [Ryan Choi]; Mr. Choi (Ryan Choi's dad); Dr. Panda Potter; Professor Helmond Kettering; Dr. Thomas Dinawa; Dr. Martin Campbell; Dean Mayland; Dwarfstar [Sylbert Rundine] (villain); Giganta [Professor Zuel] (villain); Praetor (villain); Centurion (villain)
Atom [Ryan Choi]; Mr. Choi (Ryan Choi's dad); Dr. Panda Potter; Professor Helmond Kettering; Dr. Thomas Dinawa; Dr. Martin Campbell; Amanda; Dwarfstar [Sylbert Rundine] (villains); M'nagalah (villain); The Waiting (villain); Giganta [Professor Zuel] (cameo); Faust (cameo); Silver Banshee (cameo); Monsieur Mallah (cameo); Gorilla Grodd (cameo)