He has a left cyberoptic eyepiece a prosthetic claw in his front left tentacle, a scar across his face and a blue tattoo around his right eye.
His exo-suit is much taller and wider than his brethren, and retains vestiges of Irma's "body", such as her head and arms. The head can detach and grow spider-like legs.
Irma made a cameo on April's caller ID prior to her first in-person appearance.
Irma makes her first in person appearance here, she is shown at her locker but her face cannot be seen and she has no speaking role.
Irma makes her first speaking appearance in this episode. She is shown as April's best friend, walking with her in the hall. She asks Casey where he got his bruises, and doesn't seem to like April hanging around him.
Irma appears hanging out with April, about to see a zombie movie when her friend get a call from her T-Phone. She didn't believe the "dating with Casey" excuse, and she already knew that April has some secret friends that she don't tell about. They both get hit by a pizza guy's bike, who exclaimed that he's being attacked. He leaves a pizza box, which April get it for the guys and run off. It appeared to make Irma feel bad because her friend ditched her again with no honest reason.
Irma is hanging out with April and Casey (who complains about her being a third wheel and it being a ruined date) after seeing a movie. April then senses Tiger Claw and Karai who are following them. April (who is being chased by Karai) and Casey (who gets ambushed by Tiger Claw) split up to deal with them leaving Irma confused and frustrated with the both of them and unaware of the situation.
Irma and April are captured by Ho Chan because he needed April's powers. He also says Irma has powers, but he doesn't know what they are.
After being ambushed by Foot-Bots, a panicked April takes Irma to the Turtles' Lair, believing that her best friend is trustworthy enough to keep Splinter and the Turtles' secret. There, Irma's body begins to split apart and reveals to be the specialized Kraangdroid body of Kraang Subprime, the Kraang second-in-command and a master spy who had masqueraded as "Irma" to spy on April. He says that the discovery of the Turtles' lair was what the Kraang needed to start the invasion of Earth, and he immediately opens multiple portals, allowing other Kraang directly into the lair. The living room and Shellraiser are destroyed during the scuffle, and the Turtles and April are forced to retreat while Splinter holds off the Kraang assault. Kraang Subprime is defeated, and apparently killed, when a piece of the burning derby from the lair falls on top of his unsuited body, his tentacles writhing and going limp.
Kraang Subprime survived his apparent death and his Irma-Bot suit is rebuilt. He plans to set the mutagen missile to mutate everyone in the world, but is also annoyed that it took three months to replenish their mutagen supply. Additionally, he questioned why the rest of his kind fail to speak proper English when they've been on Earth for thousands of years but gets infuriated when one of them failed to understand the question. When the Mighty Mutanimals attack, Kraang Subprime managed to set off the missile with the Turtles on it. After the missile was stopped, Kraang Subprime was forced to temporarily retreat.
He follows the Turtles to Dimension X, after a fight with the Turtles, Kraang Subprime summons the Kraang to send the Dracotroid after the Turtles. Later, he attacks the Turtles in a different Technodrome, shouting "Here's Kraangy!" as more Kraang-droids come in and fight the Turtles. However, after the Turtles succeed their mission and are teleported to safety by Dr. Rockwell, Kraang Subprime is left stranded in the Technodrome as it crashes into an island, exploding leaving only the head of his Irma-Bot suit floating around.
Kraang Subprime is revealed to still be alive, having relocated to the Technodrome which is still stranded at the bottom of the East River after two years. Kraang Prime is with him, supervising Subprime's repair of the Techndrome. Subprime finally gets the Technodrome operational and pilots it out of the water. Subprime personally defends an assault led by Bishop, the turtles and Leatherhead, which is when Bishop reveals that Subprime (or "Subsubprime") was originally a fellow Utrom. The Technodrome's show of power is short-lived, as the Triceraton Fleet begins their invasion, and the Technodrome is their first target. Bishop and his allies manage to flee the structure, but Kraang Prime and Kraang Subprime watch helplessly inside as the Triceraton Fleet easily vaporizes the entire Technodrome out of the sky. Though dead, they are only the first casualties of the Triceraton invasion, as the entire rest of the Earth and its inhabitants (save for the four turtle brothers, April O'Neil, Casey Jones) are lost at the end of Annihilation Earth, Part 2. The mass casualties are averted when time is turned back six months by the Ulixes.
Kraang Subprime is approached by G’Throkka and Y’Gythgba, who offer an alliance against the Triceratons. Kraang Subprime rejected the idea of fighting the Triceratons, stating that the Kraang mutate other worlds to get away from their mortal enemies. Upon hearing that the Salamandrians consider the Turtles worthy allies, he quickly turned on them and imprisoned them. After tracking the turtles to the Utroms' home-base, Kraang Subprime and the other Kraang attack the Utrom high council, kidnapping Queen. He and his forces then proceed to go back to their base via portals, only for Michelangelo and Raphael to follow suit. While attempting to interrogate Queen, he is beset by Michelangelo, Raphael, Sal Commander and Mona Lisa, whom after briefly fighting his summoned Dracodroid they escape to a full on battle between the Utrom soldiers and the Kraang. It is there that he is confronted by Bishop who chastises him for betraying the Utroms, reminding him he was once the Utrom hero "Knight". Kraang Sub-Prime is not phased at all by his insults, proud of his subservience to Kraang Prime. He is then seemingly killed by Bishop, only to emerge atop a Stealth Ship. Unfortunately for Sub-Prime, a Dracodroid collide with him, prompting all Kraang to retreat or being taken captive by the Utroms.
Kraang Sub-Prime hacks into Donotello's portal ray, sending them to Krang's Technodrome. It was there that it was revealed that he and Krang are cousins, and apologized for banishing him to the 2D earth of the 1987 ninja turtles. After the collective turtles make short work of their Kraangdroids, he and Krang follow them to the 2D earth to try and stop them. They then teleport back to the Technrodrome, where once again the turtles fight and defeat Sub-Prime's forces. Shortly after, the turtles reveal the that the dimensionizer would've destroyed the realities that the Kraang have been trying to mutate for thousands of years, something Sub-Prime had no idea of. He chastises Krang for his insanity and stupidity, and banishes him back to the world of the 1987 ninja turtles, shortly before the turtles defeat him and send him to the Prime Turtle dimension.
Kraang Sub-Prime, whose true name is Knight, is the only known Kraang who can speak English flawlessly, a skill he developed from his work as a spy. Unlike the other Kraang, Knight can act like a human flawlessly and is easily annoyed by the other Kraang's inability to speak English properly. He hates incompetence and often yells at his subordinates. Originally an Utrom hero, Knight betrayed them and became Kraang Prime's loyal second in command, being proud of his subservience to the Kraang leader.
- Irma possesses none of the Kraang's grammar tics, and had more organically human mannerisms than an android. When Kraang Subprime revealed his true identity, his speech continued to have the same natural grammatical constructs, not typically heard from other speaking Kraang.
- In Battle for New York, Kraang Subprime questions why other Kraang can not speak proper english as they have been on Earth for thousands of years.
- Irma wears a red hexagon-shaped bracelet on her right wrist. As seen on mutagen canisters and on the TCRI buildings, the Kraang's symbol is composed by hexagons.
- Just like all Kraang, Irma has green eyes.
- In Pizza Face, when the Pizza Guy runs his motorcycle into Irma, the collision's sound is a noticeable clang of metal against metal, foreshadowing Irma's true nature as an Irmabot—Kraang Subprime's droid body.
- In "The Invasion" April does question Irma how she can walk around in the middle of winter wearing her usual garb and not getting a cold or feeling the need to wear a coat to keep warm.
- Much like the Norman suit's design being stolen from Bishop, Kraang Sub-Prime stole the design of his android from Rook of the Utrom high council.
- His character seems to be a homage to Star Wars character Darth Vader, as both are cyborg characters that betrayed a council of noble individuals to become the right hand man of a dictator with psychic powers.
- It is unknown if Kraang Subprime still died like he did in the Season 3 Finale, since the Turtles' altered the timeline by sending him to the Turtle Prime Dimension. But since nearly everything in "Earth's Last Stand" occurred in the exact same way as the Season 3 Finale, it is safe to assume that Kraang Subprime got obliterated by the Triceratons once more, after escaping the Turtle Prime Dimension eventually.