The third member of the team seen in Power Pack is Jack Power, better known as Mass Master. Portrayed by Bradley Machry, Jack is presented as the troublemaker of the group, and he’s the one who eventually reawakens the angry ghost of Dr. Mobius for a silly game with his new friends. In the pilot, his powers are presented as similar to Ant-Man‘s, with the boy shrinking down in size to minuscule proportions… but that’s not it in the comics, and the budget wouldn’t have been able to cover an accurate portrayal of Mass Master’s abilities. Let’s see together.
The third of four siblings, Jack Power was always the wild one, since he was little. Born in Richmond, Virginia, from scientist James Power and artist Margaret Power, Jack did his best to be a handful, always making himself noticed for the troubles he got himself into. He was, however, also fiercely loyal to his siblings, and whenever someone other than himself tried to mess with them, he was always first in line to defend them. Things became a bit more complicated when the family moved to Maine, where James had gotten a new job in a governmental research facility, 
working on an experimental machine for clean and free energy. James’ work attracted the attention of some evil aliens, the Zn’rx (or Snarks, as the kids called them). The Snarks wanted James’ invention for themselves to make a weapon out of it, and they came to the Powers’ home to kidnap the whole family. A few moments later, however, a colleague of James’, Whitey, came to warn them of the incoming attack… and he got mortally wounded by the assailants. He did manage to take the children to safety, and he revealed himself to be an alien as well, a peaceful and enlightened Kymellian. Whitey offered the children the opportunity to inherit his powers, one for each of them, in exchange of the promise that they would have used them for protecting the world. Just before dying, thus, Whitey bestowed the four of them with one of his powers, and Jack got the ability to control his body mass, widening the space between his atoms to assume gaseous form or reducing it until he became an extremely solid and resistant 8” version of himself. He had just become the Mass Master, ready to try out his new, amazing abilities.
The kids decided to use their powers, for first, to free their parents from the Snarks, but they failed to prevent them from going to space on their mothership. Luckily Whitey’s sentient ship, Friday, was more than eager to help, and the four siblings left the planet to the rescue, in the first unofficial mission of what would have later become the Power Pack. Since the very beginning, Jack proved to be the more creative and versatile one with his powers, and he immediately tried to devise new ways 
to use them, exploring the potential of his newfound abilities. Even later, when the Powers found out they could exchange their abilities one with the other, Jack was so capable in handling them that he could almost immediately and intuitively find new applications even for his brother’s and sisters’ powers, actually being more capable than Alex himself in the use of his gravitational abilities. Anyway, the kids managed to save their parents, who didn’t remember anything of their experience in space due to some mind-meddling from the aliens, and Jack voted to keep even their own identities secret from them. He was the most enthusiast of the four to found the Power Pack, the world’s youngest superhero team, as he was pretty sure that this was exactly what Whitey meant when he said that they should have used their powers to save the world. Most of all, however, Jack wanted to have a chance to meet his favorite superheroes, as he had the chance to: first the Power Pack teamed up with the X-Men and the Fantastic Four, then they also met and befriended Jack’s favorite superhero of all times, Spider-Man, who albeit a little worried to see children “playing” heroes, became one of their most trustworthy allies. Jack also became best friends with Franklin Richards, and insisted to have him join the team as Tattletale, a name he came out with himself. Being a superhero was easily the funniest thing that had ever happened to Jack.
Jack Power is the typical middle child, who believes he’ll get the more attention the more troubles he gets himself into; he’s also impulsive and quite brash, always fighting and arguing with his siblings… and also with his enemies mid-fight. As Mass Master, he has the power to shrink in size to become an extremely dense and durable insect-sized midget, or to assume an intangible gaseous form, with time becoming versatile enough with this ability to turn even single parts of his body and to use both forms at the same time; he can also project what he calls a Density Field, air so compressed that becomes some sort of force field around himself or others; he can also share his life force with the other Power Pack members to heal faster, and trade powers with them, for a time going by Counterweight while wielding Alex’s powers and as Destroyer with Katie‘s ones, finding new inventive ways to use them. Always the brash type, Mass Master can truly be quite bothersome to deal with… but he’s also the one who’ll fight to the end to protect his brother and sisters, fiercely loyal to his family to the point that he’s rightfully the most feared one of the group, the one who will most likely cross the line if pushed…
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