Sparkplug Witwicky
William (or Irving, possibly William Irving or Irving William) "Sparkplug" Witwicky was a Sergeant in the US Marines. Apparently he spent some time as a prisoner of war in Korea.
He has an indeterminate number of sons (Spike, Buster and "Butch") which varies depending on the continuity. No mention ever seems to be made of him ever having had a wife.
Generation One Animated Continuity
When we first meet Sparkplug, both he and Spike seem to be oil rig workers. The rig is destroyed in the cartoon episode "More than Meets the Eye," but we never see evidence that either of them has (or needs?) a job ever again.
Marvel Comics Continuity
William "Sparkplug" Witwicky was a Sergeant in the US Marines. He was a P.O.W. during the Korean War, where he was forced to repair the Koreans' equipment. However, he secretly sabotaged that same equipment, leading to personnel and materiel losses for the North Koreans. He is a mechanic, and owned his own service station, until it was destroyed by Ratbat and the Predacons. It is never established whether or not he rebuilds the station.
Sparkplug suffers a heart attack as a result of the Autobots in The Last Stand, and is much less friendly with them than in the cartoon.
Note that in some issues, Sparkplug identifies himself as William Witwicky, and in others, he identifies himself as Irving Witwicky. The most likely answer here is that his full name is William Irving Witwicky (or Irving William Witwicky).
Dreamwave Continuity
In the Dreamwave Comics continuity, Sparkplug has been dead for several years. He was one of the humans chosen to accompany the Autobots back to Cybertron, but was presumed dead when the Ark II exploded.
