|Specifics: fictional appearances|
When you encounter Skullgrin, just who you're meeting depends largely on what he happens to be wearing at the time. The Cybertronian robot at his core is intelligent, logical, coldblooded, and vain. He tends to put his own interests above the Decepticon cause and is easily distracted from missions and even direct combat should something of interest catch his optic. He finds Earth in particular quite interesting and is eager (in a decadent and mercenary way) to learn what it has to offer him.
Should you meet Skullgrin inside his Pretender shell, however, you'll find yourself facing a whole different beast. When he's encased in its monstrous hide, a new personality takes over: he becomes a snorting, snarling, sinister sick-o. Low on brains but brimming over with boundless, unstoppable rage, this Skullgrin is the kind of warrior you just point in a certain direction and let fly. Mindless destruction is his favorite pastime, and he won't stop snarling and fighting until everything before him has fallen.
The disconnect between these two personas can lead to some rather erratic behaviour on his part. The two disparate personalities attempting to reconcile themselves within him can make who and what Skullgrin is like on any given day a toss-up, and should the coin come down wrong, a potentially deadly one for anyone nearby.
After commandeering a genetics research lab on Earth, Scorponok was able to create the science of Pretender shells using synthoplasmic chambers constructed by him and Vorath. Skullgrin was one of six Decepticon volunteers transformed by the process into Pretenders.
He was sent to Earth alone by Scorponok to construct a fuel depot in secret for his Decepticon comrades, the belief being that his organic shell would arouse less suspicion than a normal Decepticon would due to the increasing public hostility towards giant alien robots, fanned by the Z Foundation. Skullgrin caught the attention of Rollie Friendly after Bigfoot-style sightings of him appeared in the gutter press, and the film director offered him a movie role. The Pretender agreed in exchange for being paid in fuel. When the public and press went wild over him, Skullgrin began to like being a movie star. But while his Pretender shell had fooled most people, robot hunter Circuit Breaker suspected his origins. When Skullgrin revealed his true form to the movie's leading lady, the robophobic Circuit Breaker attacked and destroyed both the film and his movie career.
Following the destruction of their mobile starship headquarters, the Decepticons established a new base hidden under the New Jersey dumps. Shortly thereafter, Iguanus was chosen by Scorponok to spearhead a new energy-collecting endeavor by him and his fellow Pretenders. When Skullgrin expressed displeasure at being left with guard duty while the other Pretenders had more exciting roles, Iguanus taunted that it was because movie stardom had made him a softhearted fleshling-lover.
Skullgrin's was sent out with five of his fellow Decepticons to explore Fahl space, and their ship was attacked by the Cybertronian Empire. Skullgrin alone survived long enough to try to return to Megatron, and exploded in re-entry attempting to warn his leader.
Skullgrin was a brilliant and methodical field commander for the Decepticons. However, nobody likes intelligence in the Decepticon Empire, so his superiors put a shell program in his Pretender shell's circuitry that drove him nuts and made him virtually useless in a leadership position. And everyone lived happily ever after.
Skullgrin was one of the cultists under Bludgeon attempting to resurrect Thunderwing. When Jetfire and the Technobots came snooping around Thunderhead Pass, Skullgrin and the other cultists attacked and captured most of the Autobot scientists. When Jetfire attempted to escape his confinement, he bashed Skullgrin into a wall. Later Optimus Prime and the Wreckers arrived, Springer blew Skullgrin up with a grenade. Bummer.