Master Control

The Master Control is a program found in the Omnitrix and Ultimatrix confirmed by Dwayne McDuffie and first seen in Inspector Number 13. It adds great powers like access to aliens in Ben 10: Alien Force, and instant changes and unlimited timing in Back With a Vengeance. It can be unlocked by a special code or voice command by Azmuth, as seen in War of the Worlds: Part 1 or in a rare case by hacking.

Original Series
It first appears in Back With a Vengeance. Ben unlocks it by accident when on a boat trip. When a man falls off the boat, he uses Ripjaws to get him out of the water and Stinklfy to fly on back to the boat. He then stays Stinkfly for hours (showing off his unlimited timing) and ruins Gwen's ice cream, who's extremely annoyed by his new powers. After this, he ruins some pictures and causes more trouble until Vilgax and Kevin 11 come to steal the Omnitrix, until Grandpa Max sends them into the Null Void with Ben as Diamondhead. After a long chase, they finally get the Omnitrix until Gwen tricks them and get them back. But Ben, who turned off the Master Control, accidently transforms into Grey Matter and tries to turn back but fails. While it was the last time seen in the first series by Ben, it makes another appearance in Ben 10,000 and Ken 10, being used by the future Ben repeatedly and later also by his son Ken.

Ben 10: Alien Force
The Master Control reappears in War of the Worlds when Azmuth activates it by voice command to grant Ben all of the Master Control abilities from the original series as well as unlocking every single alien in the Omnitrix. He used aliens from the original series such as Upchuck, Way Big and Cannonbolt (and Wildmutt offscreen as confirmed by Dwayne McDuffie). After the Master Control was deactivated, these 4 aliens were appended to his Alien Force list of aliens which he used throughout Season 3. However, the Omnitrix still powered down when Ben rapidly depleted it of all of its power faster than it could recharge by turning several DNAliens back into humans from a distance. It is also revealed that he will still revert back to human if knocked unconcious.

Ben 10: Ultimate Alien
The Master Control is unlocked in the Episode Inspector Number 13 this time it is on the Ultimatrix. It has been done by hacking when 3 firewalls has been breached, but after the Ultimatrix is reseted, the Master Control is deactivated.

Trivia

 * Dwayne stated that Ben could unlock the Master Control via Voice Command, but he'd have to unlock it manually first.
 * The Master Control was unlocked during the second seasons of the Original Series and Alien Force
 * Ben used it twice to defeat the main enemy of the season (Vilgax in the original series and the Highbreed in Alien Force).
 * Logically, Ben could re-unlock the Master Control by using brainpowers of his smartest aliens, such as Grey Matter and Benvicktor (in the original series) and Brainstorm (in the Alien Force series). This can be seen in the episode Ken 10, where Ken uses Grey Matter's intellect to unlock the Master Control. If Ben had thought of this, then he and Kevin wouldn't have had to hack the Omnitrix in Vengeance of Vilgax Part 1.