Like the Utroms in the 2003 TV series, their history is inextricably, intertwined with the Turtles. It was they who attacked Splinter while he was holding the not-yet-mutated Turtles, causing them to fall into the ooze. Fifteen years later, they began kidnapping scientists with the help of a human named Snake. Their victims included Kirby O'Neil and his teenage daughter April. This was when the Turtles began to interfere with the Kraang. After the Turtles destroyed one of their compounds, mutated Snake into Snakeweed and escaped with April, the Kraang considered the Turtles their enemies.
The Turtles and April deal with the Kraang for much of the series, trying to uncover their motives and where they took April's father. In "Turtle Temper" their attempts to thwart the Kraang from breaking into a lab become complicated when a civilian named Vic catches them on video. Both the Turtles and the Kraang want this video for their own reasons, and the conflict results in Vic mutating into Spider Bytez. In "Metalhead", Donatello reverse-engineers his robot named Metalhead from a broken Kraang-droid. Later, April discovers and relates the Kraang's plans to dump mutagen in the city's water supply, prompting Don's test run of Metalhead. During the following battle, one of the Kraang is able to take over Metalhead and turns it against the Turtles, forcing Donatello to disarm his creation.
In "Monkey Brains", it is revealed that the Kraang provided Dr. Victor Falco with mutagen and offered him a lot of money to experiment with it. Falco modified the mutagen to develop a psychic neuro-chemical and tested it on his colleague Dr. Tyler Rockwell. Rockwell became a mutant monkey with psychic powers, and Falco later extracted the chemical from his brain to use on himself. The Turtles eventually saved Rockwell, defeated Falco and took his mutagen, but Falco escaped. Later in "I, Monster", Falco rants about "corporate fools" pulling his funding, implying that the Kraang were displeased with him and no longer support his research.
In The Gauntlet, more information is revealed about the Kraang. Kirby O'Neil explains that they are aliens from another dimension who brought the mutagen with them when they came to Earth. However, the physical laws of their universe are different from ours, so the mutagen does not work here the way they thought it would. In order to modify mutagen they are kidnapping human scientists, but it remains a mystery as to what they want the mutagen to do. Then in "It Came From The Depths", the mutant Leatherhead" tells the Turtles about the portal the Kraang use to travel between dimensions and he entrusts them with the power cell that fuels it.
In "The Alien Agenda", it is revealed that the Kraang are behind the Worldwide Genome Project (W.G.P.). When they receive a sample of April's DNA, they send a robotic agent named Mrs. Campbell to kidnap her, but the Turtles come to her rescue. The turtles later infiltrate W.G.P. headquarters, where they find that the Kraang have collected DNA samples from every plant and animal species on Earth. Thanks to Karai's interference, the Turtles are attacked by the Kraang and then a super-mutant that Karai creates. The battle ends with Justin's untimely demise and Karai returns to Shredder with a broken Kraang droid. From then on, the Foot Clan became interested in using Kraang tech in their war against the Turtles.
In "The Pulverizer", the Kraang are still searching for the power cell to open their dimensional portal. Donatello is keeping it hidden under a lead glass shield and using it to power his latest invention, "The Shellraiser". Unfortunately, the shield protecting the power cell is cracked when Donatello rushes to save his brothers from Fishface, allowing the Kraang to locate it and retrieve it.
In "TCRI ", the Kraang use the power cell to reactivate their portal to Dimension X. The Turtles team up with Leatherhead to get it back, and break into their headquarters in the TCRI building. The Kraang succeed in bringing Traag through the portal, and the Turtles fight him without success until Leatherhead joins them. However, both Traag and the portal survive the combined forces of Leatherhead and Donatello's homemade explosives. Leatherhead is forced to pull Traag back through the portal and the Turtles are forced to escape TCRI. Upon returning to the Lair, Michelangelo shows off a Kraang data storage device he picked up in the building. Donatello manages to decode it, and discovers some shocking information; the Kraang are searching for April.
In Cockroach Terminator, the Kraang retrieved a diamond lens for a laser drill to cause a volcanic eruption in the middle of Manhattan.
In Enemy of My Enemy, they used their portal to bring a Kraang Ship from Dimension X in order to hunt down and destroy the Turtles. After the ship was destroyed, one of the pilots was captured by Shredder.
In Karai's Vendetta, the Shredder asks the Kraang he captured why he and the others are hunting the turtles. At first, he doesn't understand it since it's out of its exoskeleton, but Karai points this out and they insert it into the exoskeleton that Karai stole during The Alien Agenda. When they put it in the exoskeleton, it refuses to answer, but then when Shredder threatens it, it begrudgingly tells him the turtles are protecting April, whom they need for their plan. The Shredder takes an interest in this and tells Karai she must find April and being her to them in order to lure out the turtles. Meanwhile the other Kraang are trying turn Earth's water into hazardous Kraang water.
In Pulverizer Returns!, the captive Kraang warned Shredder that the Mutagen is unstable in this dimension, and therefore unpredictable, and he later acknowledged to The Shredder that they have a common enemy in the Turtles.
The Kraang speak in a very complicated and redundant manner, often including the subject both at the beginning and conclusion of the sentence. They always refer to each other as just "Kraang", which may indicate the limited personality of each individual. In addition, the Kraang's human disguise always comprises of a well-dressed man in a business suit. These could be evidence that the Kraang have only a limited understanding of human culture and languages. Few (In the series premiere) don't wear that bluish coat over their exo-suits, and if they are not using their exo-suits to talk, they just screech and squeal. The Kraang also appear to be rather vain as they are very intrigued by watching themselves in action against the Turtles as seen when dealing with Vic (a.k.a. - Spider Bytez.)
- "We shall destroy the ones called the turtles who call themselves the turtles."
- "The power cell."
- "Stop the one that needs to be stopped. Stop!"
- "Kraang, the present is being a positive time to be the testing of the energy cannon."
- "Highly undesirable outcome."
- "That which is known as access is now granted to Kraang."
- "I suppose Kraang has once again been foiled by the turtles and failed to retrieve that which Kraang was to retrieve."
- "Kraang is wrong. Kraang has retrieved the power cell. In Kraang's face."
- "Kraang has been on the diet known as Gluten-Free. Kraang has already lost 13 Kraang units of weight."
- "Kraang Rules!"
- "This is definitely what is known as not good."
- "The ones known as the turtles are protecting the lifeform needed by Kraang. The one known as....April O'Neil. She is the one known as the one. She is the link that is missing from the plan that is the plan of Kraang."
- "But the substance known as water gives Kraang's membrane... wrinkly-fingers."
In the the summer of 2012, a Kraang action figure was released by Playmates as part of their first wave based on the 2012 Nickelodeon series. The figure is a faithful representation of a standard Kraang droid in grey plastic, with some pink and red detailing, and has five point of articulation; neck, shoulders and hips. The figure comes with a removable Kraang brain, a laser pistol and a laser rifle.
The card description reads:
- "Creepy, controlling and vicious, the Kraang are extra-dimensional, multi-tentacle, brain-like conquerors set on colonizing earth! To do so, they've come armed with powerful Kraang-droid exo skeletons, that (in some modes) appear human, but TURTLES BEWARE! Inside, rests a sickly, gross evil too frightening to "face"!"
In December 2012, The LEGO Group released a LEGO version of the Kraang. In 79100 Kraang Lab Escape, a Kraang appears without his exosuit. However, the set does include a mech walker in which the Kraang can be placed. Another variation appears in 79104 The Shellraiser Street Chase. In this set, the Kraang is in his exosuit. It has the same pieces as a normal minifigure, but is printed to show robotic detailing and a Kraang in the torso.
Another LEGO Kraang was released at the Rockefeller LEGO Store as a promotional set. It was released before the other sets. This time, the exosuit has fake skin and a blue suit to disguise it as a human. However, the costume is ripped, revealing the alien villainy underneath.
- They are an amalgam of both the Utroms (2003 series) and Krang (1987 series).
- In the episode TCRI it is revealed that the Kraang are after April and not her father.
- The Kraang human disguise somewhat resembles "Agent Bishop" from the previous incarnation of the show (2003 series).
- The Kraang seem to gain more understanding of humanity as the show progresses. On one occasion, this is evident in their speech when a Kraang refers to the turtles as "you" instead of "the ones called the turtles", and then refers to himself and his fellow Kraang soldiers as "us" instead of "Kraang". However, since they are around the teenage Turtles more than adults, they pick up some words from modern teenage slang. This is evident in comments like "In Kraang's face." and "Kraang is that which is known as idiotic."
- It is unknown if there are male and female Kraang, but a comment made by a Kraang in "Metalhead" ("The comment that is made by you shows ignorance of Kraang. The ones known by you as 'mother'-) indicates that they may reproduce asexually, or by some other means that does not require mating.
- Although they can handle breathing the Earth's air, they require the air of Dimension X to be able to colonize and thrive.
See: Kraang / Gallery