In their first appearance in the Generation One series, the Dinobots were dispatched to Earth to discover what had happened to the missing Ark . They encountered the Decepticons, who would become the Insecticons , and both sides blasted each other into stasis lock. The Dinobots killed Octane and stole his ship, but they ran into trouble when the local Autobot forces believed them to be traitors and fired on them. Repaired by the Autobots, who were by now convinced of their intentions, they participated in the final assault on Shockwave, where Grimlock rescued Magnus and Optimus Prime.
The Dinobots continued hiding out in the Cascades , stealing fuel from humans and sending Swoop out to spy on the Autobots at the Ark. Learning that Optimus Prime was dead, Grimlock decided to return and seize command for himself. Bursting into the Ark, he denounced Prime's style of leadership as weak and insisted only the strongest should lead but was soundly rebuffed by the assembled Autobots. Meanwhile, Ratbat , the Decepticons' fuel auditor on Cybertron, had sent Trypticon through the space bridge to annihilate the Earthbound Autobots once and for all. Outside the Ark, the Dinobots stood back and watched the slaughter for a while until Trypticon threatened Rachel Becker , a palaeontology student who had taken an interest in the local Transformer activity, which drove Grimlock to defend her. Following their leader's example, the other Dinobots charged, battling Trypticon until his fuel quota for the trip was expended and Ratbat recalled him to Cybertron. For showing courage and compassion in during the battle, the grateful Autobots then elected Grimlock as their new leader. King of the Hill!
Grimlock helped to sniff out the "dinosaur transform static" that implicated Trypticon in the theft of world monuments. Later in the year, when Decepticon leader Galvatron had Cybertron infused with function-inverting anti-electrons, a dose of the particles gave Grimlock super-intelligence. For the first time Grimlock identified himself as "I, Grimlock". During a mission to Unicron 's disembodied head, where the Autobots were outmatched by the new Decepticon Terrorcons , Grimlock used components of Unicron's head to construct the Technobots to battle them. Combined as Computron, the Technobots felt they could not match the Terrorcons, until Grimlock transferred his super-intelligence into Computron, reverting to his old self and allowing the Autobots to claim victory.