Professor Pyg is a complete and utter disturbed psychotic (created by my favorite comic book author Grant Morrison) who does all sorts of chemical and physical experiments on the innocents of Gotham City - until Batman intervenes of course.
In most of his appearances, he's just a guy in a butcher's apron and a pig mask. Wielding sharp things. I had my LEGO Butcher minifigure from many waves back set aside awaiting the pig mask, as well as a couple instruments of torture: a skill-saw and a syringe! The only other modifications made are the red hands (gloves? blood?) and the black head so you can't see Professor Pyg's face. I may be wrong, but I'm pretty sure we've never seen Professor Pyg's face in the comics. Making him all the more horrific.
I don't know what it is about a butcher in a pig mask, but it paints a pretty horrific image. I suppose it's the fear of revenge for all those bacon burgers that hits the human condition right in it's heart!
I found the newest wave of LEGO blind bagged minifigures at Toys R Us last week, and have been enjoying my completed Professor Pyg ever since. Thankfully for the rest of my minifigures, I have a LEGO Batman to keep him in line!