Some TMNT stuff really isn't for little kids.
The aliens who run the mysterious facility known as T.C.R.I., which, incidentally stands for “Techno-Cosmic Research Institute” are actually called Utroms. They are small, rather strange creatures who rely on the stubby cilia on their underside to service both as fingers and legs.
Masters of robotics, the Utroms have developed a variety of "walkers" to increase their strength and speed. Here on Earth, they use humanoid robot bodies to get around with more ease and to fit in with the human population. The aliens fit into the abdominal cavities of these robots where their cilia can easily control the robot's movements. The humanoid form is gradually replacing the older, more traditional Utrom quadruped robot. There are also specialized robot forms for the heavy construction and for precision technical work.
The T.C.R.I./Utrom are reclusive by galactic standards. Their combination of pacifism and devotion to scientific research has kept them out of the mainstream of civilization. They have explored and colonized over a large volume of space, but always abandon their possessions rather than risk exposure to more aggressive races. Within the last hundred years or so they have been pressured by the expanding Triceraton Empire, and have retreated from many of their colonies and outposts.
The aliens have been stranded on Earth for thirty years and only in the last two decades has human science and technology progressed to the point where it is advanced enough for the aliens to utilize it in making the transmat device which they hope will return them to their home planet. The Teenage Mutant Ninja Turtles owe their very existence to the crash landing of a group of the Utroms on Earth. It was one of the T.C.R.I.'s canisters of waste material (being shipped by truck to a disposal site) that accidentally started the Turtles’ mutation. The glowing ooze that the baby turtles crawled around in was actually a mutagenic microbial agent, a by-product of one of the aliens‘ experiments at producing organic circuitry. The Utroms are the peculiar aliens who kidnapped Splinter but the aliens are not hostile and are repulsed by the idea of injuring any living being. To deliberately kill an intelligent creature is totally beyond them. But are so close to reaching their goal of returning home (the transmat device is almost complete) that their violence against the Teenage Mutant Ninja Turtles was an act of desperation. They had worked so long, and were so close to returning home, that they responded with uncharacteristic alarm when the Turtles invaded their facility.