Captain Atomic’s former side-kick. Bitter and bruised over his failed coup to control Captain Atomic, Mookie is fueled by his lust for heroic stardom. He’s tired of living in another hero’s shadow (not to mention his mom’s basement) and he won’t rest until the citizens of Mega-City worship him as their one-true-hero, Sergeant Sub Atomic: The Nuclear Boy!
He appears as wide, chubby person, who has brown hair, a big pale red nose, and with long arms and short legs.
Ironically, he wears a similar incarnation to Captain Atomic, retaining some similar parts, such as a yellow helmet crest atop and a two side-winged headpiece, but he has purple head-cape with suspenders holding upon the cape and the chestplate with the "S" logo on it that has yellow shoulder caps with a star, yellow arm braces, a gray utility belt with pale blue tracings along with purple scaled undergarment and black and white sneakers.
In "Sold Out", He wore a blue short-sleeved shirt that exposes his belly, and light maroon pants with a dark grey belt with gold buckle.
As a villain, he's somewhat more of a narcissist, who's trying to be better than Captain Atomic as Atomic Puppet in terms of acting heroic, the difference being that Mookie is doing this for personal gain. In his early years, he used to work for Captain Atomic, as a sidekick, until he abruptly turned Captain Atomic into what he is now, a puppet.
There's one time where he had to rely on AP in Atomic Goo, as he was forced to help to get AP and Joey to remove the atomic super glue that AP accidentally made Joey in thinking that was hair gel. This is because AP says that Mookie won't be able to take over as being a superhero since Joey and AP are stuck together as Atomic Puppet, discouraging him into helping them.
However, it's implied that his reasoning for turning AP into a puppet was due to being mistreated back when AP was still Captain Atomic.
However in The Big Shift (Part I & II), he seems to grow tired of seeing AP and Joey get the spotlight, as he tried to devise a plan to get him back in everything, which ended up failing once again. He heavy explained to everyone that he got rid of Captain Atomic, which leads to him get arrested. While in the prison, he appears solemnly nervous at one point until one point when Professor Tite-Gripp wanted to know more of Mookie having something to do with disappearance of Captain Atomic. This led to the two concocting a plan that involves getting the rest the villains fleeing from prison and Mookie taking hold against Phil as a distraction to take AP from Joey. This leads to Joey and Phil going after him after AP was retrieved by the former. During a battle between the duo and Tite-Gripp, they kept being beaten by Mookie until they had a idea of provoking Mookie and Tite-Gripp, causing them to both come charging and collide, making a large blast radius expand. At the end, Tite-Gripp seems to have survived but with a missing arm, while dragging along an unconscious Mookie at the end.