The Atom was an ally of Batman and a friend of Aquaman.
The Atom helps Batman stop evil sorcerer Felix Faust from opening Pandora's Box in "Evil Under the Sea!".
He re-appeared along with Aquaman to save Batman from a virus created by Chemo in "Journey to the Center of the Bat!".
Atom has a Crime Syndicate counterpart called Dyna-Mite, also voiced by James Sie.
A mind-controlled Ryan Choi appears in "The Siege of Starro! Part One", demonstrating the ability to grow to giant sizes, which he uses to prevent Batman from destroying a signal leading Starro to Earth.
He also appears in the teaser for "The Criss Cross Conspiracy!", where he, Batman, and Aquaman battle the Bug-Eyed Bandit.
Powers and Abilities
As the name implies, he can shrink to extremely small sizes, the size of an atom, in fact.
He can supposedly lift things much larger than him, much like an ant.