The Mutants and Masterminds Threat Report series from Green Ronin gives a solid character with stats, Hero Lab files, an adventure hook for Mutants and Masterminds Third Edition. In the Threat Report Update, I give you some alternate views on, alternate versions of, and supplemental material for these great reports.
Threat Report #2 concerns "Junkpile", an animated pile of garbage/trash that was accidentally brought to life by castoff alien technology being struck with mysterious energies during a super-fight. Powerful but naive, it is easily tricked into serving more serious antagonists.
I often wonder why in the world origin stories of various villains and problems happen offscreen or in the background. Why not have Junkpile be created as a result of something the player characters do? Let them be blowing up alien invaders - the city helpfully hauls away the debris, not realizing that alien power sources and generators are in it. Let them be the ones who punch whatever mystic in the middle of some cult ceremony that unleashes bizarre energies into the junkyard. As with all good comic book antagonists, Junkpile is an example of the damage that can be innocently caused by the player characters' actions, so make it literally that! This will draw the PCs in and give them a personal connection to the havoc Junkpile causes.
Junk From The Stars
If the aliens whose mysterious technologies which created Junkpile return, maybe they need their engine parts back, to repair their ship and get home, or to fuel their Earth-shattering weapons. Chasing down Junkpile might be a priority for the aliens, and as he flees, the chaos he causes would be exceptional.
In My Current Campaign
Since my supers campaign recently ended, I would look to Junkpile primarily as a spiritual entity of some kind. He's been cast off by human society, sort of a pool of rejection and despairing energy, with a sulking desire for revenge. In a glossy cyberpunk world where attractiveness is available in pill form at your local mallplex, something truly ugly and perverse stands out dramatically. I certainly think I'll be using Junkpile at some point...