Mark Grayson is a typical teenager, except the fact that his father is one of the greatest superheroes known to mankind. Mark is waiting to develop his own super powers - hopefully something incredible - so that he can follow in his father's footsteps, whether that means fighting inter-dimensional aliens or stopping a bank robbery.
While Mark is at work at the local burger mart he throws a trash bag so high into the sky that it disappears. And with that, it begins!
And what better way, Mark figures, to begin than to go out and fight some crime... in a yellow bandanna goggles and a track suit. While taking down the thieving villain Titan he is spotted by his dad. Dad's impressed, but not by the costume, and Marc is taken to the tailor Art to develop a costume. Ideally, Mark hopes, something iconic.
Later, Mark sticks up for a a kid at school who is being bullied, possibly forgetting about his own strength. The principle - who he's called in to see - creates his moniker accidentally by telling him he's not Invincible.
Soon Marc is taking on some more criminals, some diamond thieves, but now he's Invincible!