Drillin is a variety of badnik created by Dr. Ivo "Eggman" Robotnik, encountered by Sonic in Gimmick Mountain Zone in Sonic the Hedgehog 2 (8-bit). Cap-wearing, caterpillar-treaded drill-bots, Drillin models leap up from the floor and try to spear Sonic with their spiky noses. Drillins are often difficult to avoid, but can be dispatched by a spin jump or spin roll.
Like other robots in 8-bit Sonic games, no animal friends pop out of Drillins when they are destroyed. Whether these badniks canonically don't contain organic batteries, or the escaping critters simply weren't shown due to programming limitations, is not known.
Drillin is very similar to (and essentially the 8-bit version of) the Burrobot badnik from Sonic the Hedgehog (16-bit), and in some sources is even called Burrobot (and also Mogurin, the Japanese name of Burrobot).
|Sonic the Hedgehog 2 (8-bit)|