He was portrayed by David Ogden Stiers.
Originally from Mars, J'onn sought refuge on Earth because Mars had none of the freedom that Earth possessed. Vowing to protect those rights, J'onn search the planet for those who gifts could help him fulfill that dream. J'onn found Guy Gardner, Barry Allen, Ray Palmer and B.B. DaCosta, and taught them how to nature and control their individual powers, and going on to form the "Justice League".
The Martian Manhunter posseses a wide variety of superhuman powers and abilities.
The Martian Manhunter posseses the power of shapeshifting, which employs for various effects (adopting human or monstrous appearance, elongating his limbs, growing to immense size, altering the chemical composition of his body, etc.).
He is a powerful telepath. He often acts as a "switchboard" between minds in order to coordinate the Justice League's actions.