Just that he has a keen eye for some of the most disturbingly freakish and awesome creatures ever seen on the silver screen. His childhood nightmares must have been some of the most traumatizing experiences ever felt by a living human. The creatures of the Hellboy series are inspired by a graphic novel, so he can't take all the credit. But, Pan's Labyrinth is just next-level out-there. I recommend checking out all of his work. Very interesting, like riding a visual roller coaster.
Can't wait to see what he does with The Hobbit... shooting starts next year