Originally slated to be Snively, but changed as Archie had that character. Entirely designed by Richard Elson, his debut appearance was issue 21, the issue before Robotnik took on his AoStH appearance. Judging from his looks, demeanour and his hunched back, its not unlikely that Richard took some cues from Igor from the old Frankenstein movies.
A lizard-like humanoid creature with mysterious oxygen tanks on his back and dressed in a scientist's long white coat, Grimer's background is a complete mystery; he simply appeared in the comic with no prior warning, however it is to be believed he has a cousin called Slimy who lives in the Special Zone, also another comic exclusive character named Proctor Speckle looks suspiciously like Grimer's race but its not confirmed he is related.
Unlike Snively, who hates Robotnik with a passion, Grimer is completely devoted to his master, no matter how many times he's been on the receiving end of Robotnik's raging fits he continued to serve him at any cost, inventing and co-planning Robotnik's schemes for world domination. He is however no fighter, weak and frail, Grimer never joins Robotnik on the battlefield, preferring to cower in Robotnik's base. When Robotnik was taken prisoner once, he tried to take over his master's place as the ruler of Mobius but failed miserably.
During Robotnik's depressive days towards the end of the comic, Grimer, in a desperate attempt to cheer up his master, unleashed Chaos upon the world, only to find out there was no way of stopping it. When Super Sonic defeated Chaos, Robotnik had truly lost his mind and, despite all he had been through, this was the last straw for Grimer, who quit. The comic ended shortly after.
Grimer's name is a play on Grima Wormtongue from The Lord of the Rings. His attitude and his role in the comic are similar, too; sneaky and evil, but an utter coward.