Board Thread:General Discussion/@comment-25400375-20141122211616/@comment-679780-20150220185959

Observer Supreme wrote: I think Grimer and Commander Brutus were interesting. If Brutus's ruthless Starscream tendencies are in Metal Sonic's personality, perhaps Grimer's hyper-competent skills can go to, if not Fang and obviously not Orbot and Cubot, then maybe a future character. I can see such a character in any future Sonic Chronicles games. I remember Grimer. I never figured out what he was.

My guess he that the machine he has on his back is a life extender machine. The device keeps him alive but does not preserve his body. And one of the reasons why he is so loyal to Dr. Robotnik is because they're both humans.

An outdated theory of mine was that Grimer is the other half of Dr. Kintobor after the accident that lead to Dr. Robotnik.