Jhiaxus - A Generation 2 Decepticon who led Liege Maximo's forces against the Autobots and Decepticons led by Optimus Prime and Megatron. Destroyed by the Swarm. Name was an inside joke "Gee Axe Us".
Jumpstarters - Two Autobots, Topspin and Twin Twist. The toys would "auto transform" when pulled back and let go in vehicle mode.
Junkion - 1) A world composed of garbage and mechanical junk. 2) An inhabitant of the world Junkion.