Although a later model of the robot, the Servatron, that eventually became Turtle X, Serling initially possessed none of its battle ability, making him a rather ineffective protector. Despite this handicap, Serling was unhesitant in risking his "life" to save Cody during his captivity inside a berserk Turtle X, and was as a result heavily damaged. Fortunately, Cody managed to repair him and reconfigure him into a new Turtle X armor, which he can now change into at will.
Serling has been taking care of Cody since he was a baby, having always been there for him, even when he lost his parents.
When Cody created a time window to view the Turtles exploits in the past, he accidentally brought them and Splinter into his time. Serling went out to retrieve them, saving them (excluding Mikey) from the Peacekeepers and giving them filters to breathe in the multi-breathing air. When they find Mikey, Serling gives him the same gear he gave the others.
When it appeared that the Turtles were going to stay until Cody could perfect the time window, Serling had to put up with them, as they made a big mess in the penthouse, smashing an antiques.
While testing out the new Holo Dojo, Serling gets infected by Viral.
When the Turtles are trapped within the new Gaminator program, Cody learns that Serling can touch them without being affected by the neural fields and uses him as a link to download some "cheat codes" to the Turtles. But when they defeat Viral, the Turtles send Serling back in the game
On Cody's birthday, everyone was prepared to keep it a secret. Serling had complied a number of video files of him and Cody but decided to erase the one with Darius. By coincidence, Cody was trapped in his own Turtle X armor being controlled by Dun. In determination to save his master, Serling downloads the anti-virus program into himself and goes after the rogue Turtle X, copying the Turtles' line, "It's ninja time", into "It's Serling time". Having learned much from them, he creates a big mess by ripping off Turtle X's right arm but gets heavily damaged before finishing the download. Cody promises to fix him and remakes him as the new Turtle X armor.
Cody and Serling disobey President Bishop's direct order to not follow him and the Turtles to Moonbase Bishop. They arrive just in time to save them from becoming Kanabo drones. Serling was also ready for Viral, trapping her with a decompiler.
- He is voiced by Marc Thompson.