Kay is a train robot created by Thomlight and Nyx themselves. He was first created when the Changelings and Deceptitrains attacked Cybertron. When, Thomas was unable to apprehend The Darkness from corrupting Ratchet, Smokescreen and Optimus, Kay came to the rescue and, using the Gem of Light, instantly freed the three Autobots from the Darkness' control. Thomas and Kay made their way to the Prison of the Deceptitrains, where they found Megatrain had been shot by an unknown villain. Lloyd Garmadon led them to the antidote that could save the Deceptitrain overlord, the now-uncoruppted Alicorn Amulet. Thomas turned into his pony form, which was the only way to activate the amulet, and using its magic, revived Megatrain. The trio then continued to the Nindroid headquarters, where they encountered Cryptor and his Nindroid followers. Cryptor attacked the trio and demanded the Element of Magic from Thomas. When Thomas told Cryptor that he would have to take the Element of Harmony from him, Cryptor threatened to kill Kay upon his refusel. Kay, however, refused to die and used his new Cyber Sword to stab Cryptor, causing the Nindroid general to deactivate. This only resulted in Cryptor's machine, which could only be generated by the power of the Alicorn Amulet, activating. Kay explained that the only way to destroy the machine was to use the Element of Magic. Thomas exposed the Element's magic from within and destroyed the machine. As a reward for his bravery, Kay was granted a position in the Autobot ranks by Optimus. Kay became a great Trainbot hero. Kay then helped Mas y Menos discover that being fast doesn't mean you have worry about losing each other. When Starscream ended up being captured, Kay worked to help rescue him. Kay, along with his friends Alf, Selly, Duck, Duke and Victor,
- Kay will be created by Thomlight and Nyx in The New Trainbot in Town.
- Kay is the fastest train in the train world!
- Kay is also only robot train who can build tunnels.