Some TMNT stuff was always meant for grownups.

Along with the Fugitoid, the Triceratons were one of the earliest creations of Mirage Studios, predating the Turtles. In the minds of their neighbors, they are really an empire that covers the entire central region of the Milky Way Galaxy, a huge interstellar domain. They are saurian creatures, possibly genetically similar to the Earth species of dinosaurs, the Triceratops. Tough and aggressive, they are entirely herbivorous (plant eating), and have a high sense of loyalty to their race. Part of the reason for the Triceratons’ aggressiveness stems from a cosmological phenomenon occurring in the heart of their region of space. There is a region of destructiveness that is gradually spreading out from the hub of our galactic spiral. The exact cause of this stellar disaster is not known. The Triceratons deny any problem and laugh off the idea of a killer Black Hole. However, many stars in the region have gone nova, and there are accounts of refugees arriving at the outer Triceraton worlds. The best evidence of the galactic holocaust are the Triceratons’ asteroid homeworlds. Hugh asteroids are outfitted with gigantic ion drives and become mobile cities and military staging grounds for the expanding Triceraton empire. Special asteroids are dedicated to factories, universities, research centers, and even arens for sporting and gladitorial events. The Triceraton Republic is now engaged in an ongoing conflict with the Human Federation ("Federat"). A border region consisting of thousands of square light years has each side jockeying for position. Currently, the open warfare has subsided, as both sides continue searching for a weakness or a weapon to solve the impasse. There are many reasons for the success of the Triceratons. First is their eagerness to adopt new technology, and their willingness to change their tactics accordingly. A specific technological strengths that the Triceratons have exploited thoroughly is their atmospheric adaptability that allows them to self-mutagenically breathe otherwise unsuitable air. Some Triceraton agents take Xemorene, a highly addictive stimulative drug that increases speed and efficiency of the nervous system, the withdrawal effects leading to heart failure and death. In the aftermath of the Turtles’ accidental transportation to Triceraton space (during which time the Turtles competed in a combat tournament against four Triceratons in a "Tri-Sports" bout, then took the Triceratons’ Prime Leader hostage) upon their breaking into the TCRI building, three were accidentally transported along with the Turtles back to Earth (TMNT Vol. 1, #6 & 7). While one of them was captured by DARPA (TMNT Vol. 2, #9 - 13), and another, Zog, went into hiding in the sewers until Raphael discovered him prior to the Turtles’ second confrontation with The Shredder (TMNT Vol. 1, #19 & 20), the third transported Triceraton remains unaccounted for. After their accidental sojourn into Triceraton space and D'Hoonib, the Turtles were invited back to the TCRI homeworld, where they were reunited with the Fugitoid. Almost immediately after they arrived, Gavat-4 Station, an outpost that had a Transmat link directly to the Utrom Homeworld, fell under heavy Triceraton attack. The Turtles agreed to help them, transporting themselves to the station and self-destructing it (TMNT: Guide to the Universe, Shell Shock). When the Turtles pursued DARPA in search of their brother, Raphael, missing after a conflict with a then-cyborg Dr. Baxter Stockman, they soon found themselves facing a Triceraton invasion in Nevada. The cityship that made up the invasion force (it followed the Turtles’ transportation signal from when they were accidentally transported there), falling apart from its long space voyage from Triceraton space, attempted to ram and decimate the Earth by slingshooting around the sun and engaging full Impulse Speed. This attempt, however, was presumably stopped by Louis Braunze’s extraterrestrial-captured "inter-phasic cannon," which he planned to use to move the Triceraton cityship out of phase, causing it to then harmlessly pass through Earth’s outer crust and re-solidify in the molten core, vaporizing the gigantic vessel (TMNT Vol. 2, #13).