Mad Jacks

"You got a mission? Don't sweat it. We'll crank it up to Jacks-imum overdrive! Jack attack!"

- Greg Jack saying the Mad Jacks' sales pitch. "Jacks rule!"

- The Mad Jack's catchphrase.

The Mad Jacks are minor antagonists in Big Hero 6: The Series. They are a group of destructive, high-tech mercenaries who take on dangerous missions in an "extreme" manner.

"Greg" Jack is voiced by Rob Riggle, Jack is voiced by Kevin Michael Richardson, and Jaq is voiced by Kerri Kenney.

History
In "The Impatient Patient", the Mad Jacks are hired to steal a hard drive that Alistair Krei purchased on the black market. The three then attack Krei on his yacht, but are intercepted and foiled by Hiro and Baymax, although Hiro develops the flu as a result of their fight. The Mad Jacks are later contacted by their employer, Obake, who berates them for losing to a child and orders them to finish the job. Later, Fred researches the Mad Jacks and informs Hiro, GoGo and Honey Lemon that they are a shadow ops team who not only have their own website, but theme song as well.

Meanwhile, Krei has finished doing the same research on the Mad Jacks, and, as he prepares to have the chip probed, Jack and Jaq crash into his window. Krei remarks that his windows are impenetrable, his assistant asks if his windows are the only thing that is impenetrable, as Greg Jack rockets through the floor and kidnaps Krei. While they are making off with Krei, Jack grabs Hiro as he is trying to pursue them alone and drops him into a dumpster, breaking his leg in the process.

The Mad Jacks take Krei back to their headquarters, a mobile airship, and force Krei to hand over the drive before hanging him off the Krei Tech building. The Jacks then head to Obake's lair, where Greg Jacks hands him the drive. Obake then notices that Big Hero 6 is approaching and Greg Jack opts to distract the heroes while he gets away, although, since Obake prioritizes the drive's security over all else, Greg Jack decides to hold on to it instead. The Mad Jacks then engage Big Hero 6 in a fight, and, after Greg Jack takes Baymax out with a giant cannon, Hiro intervenes using a robotic duplicate of himself and helps his friends fight the Jacks off. Hiro and Baymax soon take the drive back from Greg Jack, but are unable to prevent him and the other Jacks from escaping. Ultimately, it is revealed that selling Krei the drive and hiring the Jacks to "steal" it was all part of Obake's plan to trick Krei into using it without having it checked, resulting in him gaining secret access to all of Krei's files, including one revealing Hiro's secret identity, through a bug in the chip.

Trivia

 * It is unknown if all the Mad Jacks' real names are actually "Jack", or if they all use Jack as a codename, considering the Jacks' leader's real name is Greg, while the other Jacks go without confirmed names.