|“||Now that I know where that robot will be, I can destroy MECH-X4 in front of it's biggest fan.||”|
— Principal Grey
Kim Grey was the principal of Bay City High. She appears nice and caring, but in fact is the one deploying the monsters against the city. She was working for Seth Harper, an evil mastermind bent on destruction, but she never knew her boss's identity.
She is portrayed by Ali Liebert.
In Let's Call It MECH-X4!, she is the principal of Bay City High to keep her identity safe. She launches a first monster at Mech-X4 and they manage to defeat it successfully. When she saw on the news that Mech-X4 is going to be with Seth Harper, she launches a second monster to be waiting for them when they get there.
In Let's Get Some Air!, she hires Davage to stop them getting the ooze from the volcano to cure Harris. She also finds out from Davage that there are pilots on board Mech-X4. Principal Grey reports back to The Mastermind that there are humans on Mech-X4.
In Let's Open The Monster Heart!, Principal Grey and Davage are planning a monster who can destroy the humans on Mech-X4. She realizes that Mech-X4 have the Primorphous Gel from the Jaguasaur monster. Principal Grey gets a signal when Ryan and Spyder activate it. At Bay City High, Principal Grey instructs Davage to put the new Primorphous Core to the checkpoint where the Primorphous Gel is. Principal Grey now knows where the Primorphous Gel is and she knows that it is at Harper Futuristics. Principal Grey goes back for the Primorphous Core in a disguise. Whilst Ryan was getting the monster core, he found the person who was sending Mech-X4 monsters, but didn't see the face. Mark finds Ryan and Principal Grey threatens he's going to hurt him if Ryan doesn't give the Primorphous Core. He gave the Primorphous Gel to her and she disappeared. She also finds out that Ryan is the person who controls Mech-X4.
In Let's Be Idiots!, Principal Grey is talking with Davage through her Monster Desk. Grey talked to him that Ryan was going to the Bay City Skate-Off, about who the other pilots are and where the robot is. Later, Davage is with Principal Grey monitoring what Ryan was doing at the skate-off. When they monitored Ryan, Davage noticed that Ryan spent a lot of time with Spyder and wondered that they should eliminate every single child in Bay City High. Before Principal Grey could answer, the Mastermind interrupted. Grey used Jaguasaur's Primorphous Core to bring him back. However, she added upgrades to Jaguasaur. Principal Grey devised a plan to put a tracker at the skate-off on Ryan and managed to complete her plan. After the monster fight, Grey used the tracker and it led her straight to the Abandoned Ferry where Mech-X4 is.
In Let's Get Our Robot Back!, Davage lost Mark and she realized that The Mastermind was coming. When Ryan, Harris and Spyder activated Mech-X4, Grey fired Jaguasaur at them. Later, Grey met Grace to talk about Ryan's grade. When Grace left, Grey talked to Ryan that The Mastermind wanted to eliminate her and needed Ryan's help.
In Let's Get the Big Bad!, Principal Grey was working with Ryan to defeat the Mastermind. At Bay City High, Principal Grey convinced the Mastermind to give her a second chance. At night, Principal Grey was still at Bay City High. She found Morris and learnt that Morris was another agent working for the Mastermind. More guards came and Ryan, Harris, Spyder and Mark came to help. The guards retreated and Ryan took Morris' phone. When Mech-X4 reached the Mastermind's location, he sends Clawboon. Grey double crossed them when she turned off Mech-X4's main battery. Whilst Ryan was using the X-Weapon to destroy Clawboon, Grey escaped. Ryan, Harris, Spyder and Mark found her. Ryan and Mark fought her and hanged on Mech-X4. Principal Grey couldn't hold on and slipped into Clawboon's ooze.
In Versus The New Evil, Grey stole one of the trucks that was carrying ooze in it. Grey went to a warehouse. Grey turned into a monster to fight Ryan, Harris, Mark and Spyder. She left with the ooze because she didn't want to get caught.
In Versus The Deep, Grey told Seth, who she held prisoner, she didn't get the giant Primorphous Core, but she got the component she needed.
In Versus The Outbreak, two weeks earlier, it was revealed that she captured Seth to make the same Primorphous Gel that Grey fell into. She needed to test it so she decided to test it on East Bay City High. Grey sneaked into East Bay City High to mix the gel with the chocolate in the kitchen. Grey made Seth make another similar gel without the weakness of the Cold Cannon.
In Versus Harper's Ghost, Grey was waiting for Seth to give more ooze so she can give it to Traeger. Grey saw that Ryan, Harris, Mark and Spyder knew her location so she turned into a monster only to be found out that there was an ooze antidote which de-transformed Grey back into a human. Harris was making sure Grey didn't go anywhere, but she left Harris and Harris stated that he lost her.
In Versus The Dark Night, Grey summoned the monster back after it took all of Mech-X4's energy and inserted it into Traeger. Grey questioned why Traeger didn't destroy the robot but he reminded her what his purpose was.
In Versus The Tech Army, Grey was with Traeger. They were at the airport and stole polymine which protects weapons during cold weathers. Grey took it via plane to the Secret Government Weapons Facility.
PersonalityShe appears to be nice, but is actually the one behind the monster attacks. When one of the monsters she created lost a battle to MECH-X4, she became extremely angry, showing that she has a short temper.
- Monster Desk: Principal Grey has a desk located in her office which allows her to merge two creatures or creatures' D.N.A. together to create a monster. It glows orange when in use, just like the goo the monsters are made of.
- Ninja Skills: Principal Grey is very flexible and very good at combat fighting. This was shown when she fought Ryan in Let's Open The Monster Heart!.
- Monster Ooze: In Versus The New Evil. It is shown she had returned, after falling into Clawboon's ooze. It is also shown that she now can transform from human to a monster, and back. She can also resist a lot of damage.
- Let's Call It MECH-X4!
- Let's Get Some Air!
- Let's Open The Monster Heart!
- Let's Be Idiots!
- Let's Survive in the Woods!
- Let's Get Our Robot Back!
- Let's Get the Big Bad!
- Let's Dig Deep! (flashback)