He was just a random Druddigon guard with nothing interesting setting him above the other NPCs, but everything changed when the dragons attacked. He wound up getting assigned to keep track of some young humons, including Silentran♂… and that's where his pain begun, as the humon proved to have a very good innate ability to be annoying and "Vehicle" was bound to carry him around to places and help him reach high stuff.
Eventually "Vehicle" got so fed up that he yelled at him in the middle of the chamber where Reshiram and Zekrom stood. Fortunately this did not end up with him getting punished. For his own sanity, he ended up shaking Silentran♂ off and punting him to Milo, much to the displeasure of the ottermon (and of Maekrite, who was there looking), and then he ran away as fast as his legs could carry him.
There is a universe (which might or might not be the OU) where "Vehicle" is attached to a Trainer, who named him Mack.