Interestingly, the Mac Mini motherboard assembly was dwarfed by the iMac G4's original 3.5-inch HDD. This made the mod easier, and space helped retain the optical drive functionality.
Apple iMac 'iLamp' Mod Brings M1 to G4 : Read more
Apple iMac 'iLamp' Mod Brings M1 to G4 : Read more