In 2002, George Lucas conceived of General Grievous as a powerful new villain for Revenge of the Sith, specifically envisioning the character as a cyborg droid general to reflect and foreshadow Anakin Skywalker's transformation into Darth Vader at the end of the film.[1][2] The only instruction Lucas gave his art department was to make the character "iconic" and "scary".[1][2] Numerous illustrations were developed at Lucasfilm, some purely mechanical and others more alien-like in appearance. One drawing presented Grievous as an eight-year-old alien child on a hover chair guarded by two IG assassin droids, which Lucas rejected for not being threatening enough.[2] Another rejected robotic design was ultimately used for Grievous' IG-100 MagnaGuards in the film.[2]

Two weeks after Lucas' instruction to design Grievous, a sketch made by concept artist Warren Fu was chosen and developed by Lucas for the character's finalized appearance.[1] Fu took inspiration from the top view of a spray bottle for the design of Grievous' face.[2] Fu's sketch was made into a 1-foot (30 cm)-tall maquette sculpture which was then refined into a realistic computer-generated model by Industrial Light & Magic (ILM). This was one of the most complex models ever created by ILM at the time as many of its components were of differing physical qualities. Comparisons have been drawn between Grievous' appearance and Jacob Epstein's sculpture Rock Drill.[3][4]