Skullgrin is a minor antagonist in the G1 Transformers franchise. He was based on a figure from the 1988 toyline, so his appearances are largely confined to the comics.
Skullgrin was one of the Decepticons who accompanied Scorponok to Earth. Shortly after their arrival, he and five others underwent the new Pretender process, being fitted with hardened Pretender shells which disguised their robotic nature and made them appear like giant monsters. Their first mission was less than successful, as they ended up being defeated by the Autobot Pretenders thanks to the guidance of Optimus Prime, whose mind was stored on a computer disc at the time.
Scorponok sent Skullgrin out alone to establish a fuel depot for the Decepticons on Earth. His tactic of hiding in the woods and scaring people proved oddly effective: He was found by a film crew who wanted him to start in their latest movie and agreed to pay him with fuel. He struck up a friendship with the film's leading lady, Carissa Carr, and revealed his true nature to her. However, this resulted in him being attacked by the anti-robot vigilante Circuit Breaker. Skullgrin initially believed Carissa had betrayed him and was prepared to let her fall to her death until Circuit Breaker put him straight. Circuit Breaker still wanted to destroy him, but the fact that the director, Rollie Friendly, was so delighted at the prospect of filming Skullgrin's death was enough to put her off and depart leaving Skullgrin injured.
Skullgrin rejoined the other Decepticons and participated in the battle with the Underbase-powered Starscream: He was one of the few Transformers to survive the battle, since his organic Pretender shell protected him from Starscream's blasts. However, he wasn't entirely trusted by the other Decepticons, who considered him a "fleshling lover". When Scorponok assigned key roles to the Pretenders in his plan to cause an electrical storm and then harvest the power of the lightning, Skullgrin's task was to stay in a swamp guarding the storm generator. He objected to Iguanus killing the lone human Cecilia Santiago, but had few qualms about the fact that the storm striking New York City would likely cause thousands of deaths. In the end, the plan was defeated by the Autobot Micromasters.
Skullgrin continued to appear with Scorponok's troops through to the brief civil war against Shockwave's rival Decepticon group. Since he was last seen charging into battle, he may have been deactivated during the conflict.