Sparkplug is Spike Witwicky's father. He is described as a widower in the show bible. In addition to being a highly skilled automotive mechanic and engineer, "Sparkplug" Witwicky (for whom no real name was offered in the cartoon) had, in his lifetime, also worked in the crystal mines of Burma, and was working on an oil rig with his son, Spike, in 1984 when a Decepticon attack brought the Transformers into his life. Rescued from drowning by Optimus Prime, Sparkplug became a friend and ally to the Autobots, mainly excited at the prospect of encountering and learning about strange new alien machines and technology he could work on.
A frequent mechanical assistant to Ratchet and Wheeljack, Sparkplug is skilled in physical, practical arts, but like many fathers, lacks knowledge about his son's esoteric tastes, such as types of music, and dinosaurs. Sparkplug owns an automotive garage in New York, which the Autobots refitted to serve as a secondary command base while they were far from their main headquarters.
Aside from helping Bumblebee to plant a bomb that disrupted the Decepticons' crystal-mining operations in Burma, Sparkplug's biggest role in any Transformer adventure was when he was captured by the Decepticons and became the first subject of Doctor Arkeville's mind-controlling hypno-chip. Under Decepticon control, Sparkplug sabotaged many of the Autobots under the preface of repairing their systems, and was later taken to Cybertron to toil there under Shockwave's command, until Wheeljack successfully created a device to undo the hypno-chip's effects.
Sparkplug was never seen or referred to again after the second season of the original Transformers cartoon series, and it is possible that he died or retired at some point between the second season and Transformers: the Movie, which took place 20 years later.