Sparkplug Witwicky is a construction worker in New Detroit.
Sparkplug was overseeing two construction bots in a mine, being paid by Isaac Sumdac to find something. Only problem was, that something found them...and it had friends. Sparkplug was attacked, and was presumed dead.
Except he got better. While the Autobots were looking for Scrapper and Mixmaster, the Autobot Bumblebee thought that Sparkplug's truck was Mixmaster, and fired several bursts from his stingers, which did nothing to damage the truck. Upon being attacked by another alien lifeform, Sparkplug displayed both calmness and familiarity with modern slang by asking "Dude, why you whaling on my truck?" after Bumblebee's attack. Guess that encounter in the mines wasn't as bad as we thought.
Later, he drove an oil tanker and got mugged by the Constructicons.